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F EDERAL R ESERVE B ANK

OF

P HILADELPHIA

Second Quarter 2020
Volume 5, Issue 2

A Ticket to Ride
Central Bank
Digital Currency
House Price Booms,
Then and Now
Research Update
Q&A
Data in Focus

Contents

1

Second Quarter 2020 Volume 5, Issue 2

A Ticket to Ride: Estimating the Benefits of Rail Transit
From 1990 to 2000, Los Angeles spent $8.7 billion to build 46 train stations and four
rail lines. Chris Severen calculates their commuting and noncommuting benefits.

10

Central Bank Digital Currency: Is It a Good Idea?

A publication of the Research
Department of the Federal
Reserve Bank of Philadelphia

16

House Price Booms, Then and Now

Economic Insights features
nontechnical articles on monetary
policy, banking, and national,
regional, and international
economics, all written for a wide
audience.

22

Research Update

28

Q&A…

The views expressed by the authors are not
necessarily those of the Federal Reserve.
The Federal Reserve Bank of Philadelphia
helps formulate and implement monetary
policy, supervises banks and bank and
savings and loan holding companies, and
provides financial services to depository
institutions and the federal government. It
is one of 12 regional Reserve Banks that,
together with the U.S. Federal Reserve
Board of Governors, make up the Federal
Reserve System. The Philadelphia Fed
serves eastern and central Pennsylvania,
southern New Jersey, and Delaware.

A central bank digital currency may be the next big thing in personal banking. Daniel
Sanches evaluates the costs and benefits of this new technology for individuals,
banks, and the entire economy.

In the early 2000s, house prices boomed—and then crashed—in some places more
than others. Burcu Eyigungor evaluates two competing explanations and explores
the likelihood of a repeat.

Abstracts of the latest working papers produced by the Philadelphia Fed.

with Chris Severen.

29

Data in Focus
GDPplus.

About the Cover
Tariff

Patrick T. Harker
President and
Chief Executive Officer
Michael Dotsey
Executive Vice President and
Director of Research
Adam Steinberg
Managing Editor, Research Publications
Brendan Barry
Data Visualization Manager
Natalie Spingler
Data Visualization Intern

ISSN 0007–7011

A tariff is a tax placed on imports. This issue's cover depicts the economic costs and
benefits of tariffs. The horizontal axis represents the amount of a good consumed by
an economy; the vertical axis represents its price. The bottom horizontal line
represents the price and supply of that good if there is no tariff. As you can see, without a tariff, there's plenty of supply at a rather low price. A tariff, however, should
raise the price and decrease the supply. Each of the upper two horizontal lines
represents a different tariff level. In other words, a tariff lifts the horizontal line—and
thus the price—to its new location, but it also reduces consumption of that good.
This graphic helps economists measure the new tariff's consumer loss, producer
gain, and government revenue gain—each of which is depicted by different, and at
times overlapping, polygons.

Connect with Us
We welcome your comments at:
PHIL.EI.Comments@phil.frb.org

Twitter:
@PhilFedResearch

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Previous articles:
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LinkedIn:
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Photo: anouchka/iStock

Chris Severen is a senior economist at the
Federal Reserve Bank of Philadelphia. The views
expressed in this article are not necessarily
those of the Federal Reserve.

A Ticket to Ride

Estimating the Benefits of Rail Transit
Starting in 1990, Los Angeles County built a new and expensive
rail transit system. Now we can calculate the costs and benefits.
BY C H R I S S E V E R E N

T

ransportation infrastructure shapes the spatial
fabric through which we thread our daily travel.
How do we get to work or to school? Where
do we go shopping? How long does it take to meet up
with friends? Is it worth driving or taking rideshare?
Public transit systems—including buses, streetcars,
rail lines, and ferries—play a key role in determining
our daily travel patterns. Rail transit (subways, light
rail, and regional rail) has traditionally been important in older northeastern cities like New York and
Philadelphia. Since the 1970s, though, many other
cities in the U.S. have sought to increase the mobility
available to their residents by building rail transit
infrastructure, too.
Building rail is costly and requires large initial
public investment. Do the benefits of rail infrastructure outweigh their high costs in younger, more
automobile-oriented cities? This is an open question

LA METRO RAIL IN 2000

Lines

4

Stations

46

Average Weekday

174,554
Ridership

860,579
Passenger miles
Source: 2000 National
Transit Database.

A Ticket to Ride: Estimating the Benefits of Rail Transit

2020 Q2

in the U.S., where many cities are polycentric (they
have many employment centers rather than a single
urban core) and typically not very dense.1 These
factors limit how easy it is for rail transit to connect
home to work and other destinations. It is difficult
to cost-effectively serve a disperse population that
travels to disperse locations with public transit.
Further, rail transit infrastructure tends to be very
costly in the U.S.
In this article, I discuss why mobility is important
and provide an overview of the different ways
economists measure the benefits of transit infrastructure. I then describe my hybrid approach, in which I
combine three of these methods to study the value of
rail transit in Los Angeles.2 I conclude by conducting
a cost-benefit analysis of the first wave of Los Angeles
Metro Rail and interpreting the results of this analysis.

Federal Reserve Bank of Philadelphia
Research Department

1

Why Does Mobility Matter?

Mobility allows people to access places. The more
mobile they are, the more options they have: They can
get to more jobs or schools and choose between
more places to shop and find services. Being able to
access many different workplaces, consume varied
goods, and meet with lots of different people is one
of the big advantages of living in a city. (Before the
modern era of automobile and rail infrastructure—that
is, when everyone walked or traveled by horse—most
firms were small and people worked and consumed
more locally.3) Even our network of friends depends
on the transportation network.4
Greater mobility allows cities to be larger, enabling
the comparative advantage of cities in productivity,5
and one of the most important components of urban
mobility is commuting: how workers get to their
jobs. Cities let workers connect with a variety of jobs,
and firms with a variety of workers. Diverse, productive labor markets make cities the engines of
economic growth.6
Commuting behavior depends on available
transportation infrastructure. Indeed, much transportation infrastructure is designed with peak
commuting capacity in mind. (Commuting is, after
all, an everyday activity essential to the function of
urban economies.) People and firms benefit when
this transportation infrastructure makes commuting
easier. As an extreme example, in their 2015 paper
Ferdinando Monte and his coauthors calculated that
prohibiting commuting across county lines would
decrease aggregate welfare by 7.2 percent, and the
effect in central cities (like Manhattan) would be even
greater. Better transportation infrastructure can
directly increase employment growth. In their 2012
paper, Duranton and Turner showed that cities with
more highways in 1983 gained substantially more
employment by 2003 than cities with fewer highways.7
And transportation infrastructure can address (or
exacerbate) certain inequalities. For example, long
and challenging commutes may affect women more
than men: Women tend to work less in cities with
very high congestion and long commutes (like New
York City) than in cities where commuting is relatively
easy (like Minneapolis).8

Transit is valuable also because it enables mobility
without automobiles. Some people, because of age,
disability, or preference, are unable to drive automobiles.9 Automobiles can be very costly; households
with automobiles on average spend 4.3 times as much
on transportation as households that do not use
automobiles.10 There are other consequences of automobile use: They are land- and energy-intensive. The
average energy cost for automobiles is about 3,180
British thermal units (BTUs) per passenger mile, while
urban subways and light rail use only 24 percent of
that energy per passenger mile.11 Moreover, cities with
subways tend to be denser, so the average trip distance
is shorter.12 Because cities that rely on the automobile
tend to contain more low-density development,
they have a higher carbon footprint.13 Finally, automobile use can lead to severe congestion in cities,
causing substantial delays and decreasing mobility in
some settings (Figure 1).

How to Quantify the Benefits of Transit
Economists use several methods to evaluate the benefits of transportation infrastructures, and rail transit
in particular. Each method has both advantages and
disadvantages.

Transportation Spending
for Automobile-Owning
Households

×4.3
compared to nonowning
households

Energy Cost of
Automobiles

3,
180
BTUs per passenger mile
Energy Cost of Urban
Subways and Light Rail

763
BTUs per passenger mile
Density Decreases from
Downtown
‘000 people/mi² vs. miles
from city hall, 2010
Philadelphia vs
Los Angeles
Population
35

Hedonics
The hedonic approach compares real estate prices
near and far from rail. The intuition is that if (identical)
people value transit, they are willing to pay more to
live near sites of transit access (like subway stations).
This increases the demand for residences near transit
stations, which then increases the price of nearby
housing. This is particularly true if the supply of housing is relatively fixed, and if transit connects people
to where they want to go.
In practice, there are several challenges to simply
comparing home prices next to and far from transit.
Houses or neighborhoods near transit are often substantially different from those further away; they may
be older (or newer), denser, or surrounded by a different set of urban amenities (such as restaurants and
schools). Real estate prices also reflect expectations

0

1

Miles

55

Source: U.S. Census.

FIGURE 1

Commuting Modes Compared

Autos' flexible departure times come at the price of congestion.
Commuting by Subway or Light Rail

Commuting by Automobile

Scheduled
departure times:
Commuters can
travel only at
specific intervals
from fixed places

Scheduled arrival times
to fixed locations
Consistent travel times

Federal Reserve Bank of Philadelphia
Research Department

Commuting by auto
means one can
depart at anytime
from anywhere

Congestion:
Rush hour traffic
may extend total
travel times
Time

Time

2

Commuters have a wider range
of times in which to travel

A Ticket to Ride: Estimating the Benefits of Rail Transit
2020 Q2

about future change. This muddies the interpretation of price
gradients near transit. If prices increase in expectation of a transit
station opening (that is, before it opens), it could simply be that
people expect increases in (nontransit) amenities nearby. So the
belief that transit will generate value can make it appear that
transit is valued.
It can also be hard to separate the different effects of transit
from real estate prices. There may be a mobility benefit that
people value, but some real estate price appreciation might
instead be due to related transit-oriented development, as new
and potentially valuable amenities (such as restaurants and
stores) move into an area. Or there could be offsetting negative
effects of transit due to the possibility of noise, pollution, or
crime.14 At-grade transportation infrastructure can even serve as
a barrier separating neighborhoods from other nearby locations.15
Careful research design can overcome some of these challenges.16
A final challenge with the hedonic approach is that it can
be difficult to study demand linkages across space. If people
demand more housing near transit and prices rise, these higher
prices might cause some people to move to other slightly more
distant areas, increasing housing demand and prices in those
neighborhoods. The hedonic approach typically compares places
with and without transit, and so it misclassifies places without
transit as unaffected even if they are indirectly affected by transit.

Modal Choice
Another method compares the relative proportions of people who
use different commuting modes to get between similar locations.
(Automobile, bus, rail, and walking are all different modes.)
By comparing the characteristics (like travel time, average delays,
and cost) of the trips that take place on each mode, researchers
can calculate how much commuters value these characteristics.
For some trips (or along some routes), transit is faster, while for
others cars are faster. Comparing these characteristics and
the number of people who choose each mode tells us how much
people value fast travel, or how much benefit they receive
from different trip characteristics. For example, many people
value listening to the radio while driving, or reading the paper
(or checking Instagram) while riding the train or subway more
than they value the speed of either option.
An advantage of this approach is that it can be implemented
with a survey, so you can simply ask people about the characteristics of the choices they face and perhaps even the reasons
for the choices they make. One challenge with this approach is
that researchers must typically assume that they have described
all the factors that underlie people’s decisions on how to commute. In practice, this can be hard. Many transit modes have
highly variable travel times or require waiting for long periods.
Both are factors that people particularly dislike, yet both are
often ignored.

City Structure
A key tradeoff that drives city structure (and where households
and firms choose to locate) is access versus price. Transportation
infrastructure allows people better access to inexpensive land.

Rail transit does this in a different way than roads, concentrating
the benefits of access near transit stations.
People’s choices about where to live and work reveal that
access is valuable. Aggregating the commuting behavior of people
who live in a neighborhood or work in a particular area yields
an interesting (though perhaps obvious) conclusion: On average,
closer locations have more commuting between them. Economists call this phenomenon gravity, and they have started
building spatially explicit models that incorporate this behavior
in powerful ways. By combining the notion of gravity with
modal choice and transportation data, researchers can estimate
the value of increased ease of travel due to transportation
infrastructure.17
This approach enables researchers to build relatively complex
economic models that capture many significant features of urban
economies. Moreover, these models typically capture how
people move in response to changes in local neighborhoods or
commutes. The fact that people move links the demand for
housing across space, and can cause local housing prices to
reflect changes in other neighborhoods. If this occurs, the hedonic
approach will not correctly value these local characteristics, but
these more complex models will.
However, this literature has typically assumed that transportation infrastructure only shifts travel outcomes, ignoring
other effects it may have. As discussed above, transportation
infrastructure can potentially change the quality of residential
amenities in a neighborhood or come packaged with zoning
policies that increase (or decrease) housing supply. Another
challenge facing this literature is that it usually requires a big
shock to a city to estimate the models. For example, in their
2015 paper Gabriel Ahlfeldt and his coauthors used the division
and reunification of Berlin to estimate their model. It can be
challenging to study less extreme settings.

A Combined Approach
Given the different strengths of each of these approaches, there is
value in combining them. In my 2019 working paper, I bring
together components of these three methods to calculate the
total benefits of rail transit. I use spatial data on commuting
behavior to directly estimate the commuting effect of transit.
I then combine this with hedonic-type estimates of the residential
and workplace effects. Finally, I put this all into a model to
account for other spillovers across space (Figure 2). The total
effect can be decomposed as follows:
Total Effect = (Commuting Effect + Residential Neighborhood
Effect + Work Neighborhood Effect) − General Equilibrium
Adjustments
I study rail transit in the greater Los Angeles area (Los Angeles
and adjacent counties), which has some features that make it
particularly valuable as a research subject.

Transit in Los Angeles

The case of Los Angeles offers a number of useful features to
evaluate transit. First, greater Los Angeles had no subway or
light-rail transit at the beginning of 1990, and it built a relatively

A Ticket to Ride: Estimating the Benefits of Rail Transit

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

3

FIGURE 2

Decomposing the Total Effect

There are intermediate steps between
the opening of a transit station and an
increase in ridership.
New Transit Station Opens in the Neighborhood

← Downtown

New transit station opens

People Begin to Move In

large system within 10 years.18 By 2000,
Los Angeles Metro Rail consisted of 46
stations on four lines.19 This means that
it is possible to compare the detailed
geography of commuting in Los Angeles
before and after rail transit was available.
The relatively large system size matters,
too. For statistical reasons, it is harder to
detect incremental changes if a city adds
a few stations (or one line) every decade.
Furthermore, there are network effects
to transit—the more stations there are
(or places that are connected), the more
useful the system is and the bigger the
benefit.20
There’s another reason to study Los
Angeles Metro Rail. It’s relevant for the
many automobile-oriented cities considering new subway or light-rail systems.
Los Angeles has historically been a poster
child for the automobile. It faces many
of the transportation issues common
to cities that came of age during the automobile era.

Commuting and
Noncommuting Effects

−

Population

+

New Restaurant Opens in the Neighborhood

New restaurant opens

Home Prices Start to Increase

−

4

Prices

+

Federal Reserve Bank of Philadelphia
Research Department

To measure the commuting effects of Los
Angeles Metro Rail, I use Census Transportation Planning Project data on the
number of people who commute from
each residential neighborhood to each
workplace. I define a neighborhood as
a census tract, a unit of measurement used
by the Census Bureau.21 I use data for two
years, 1990 and 2000, so that I can look
at changes in how many people commute
between two tracts. This helps limit the
confounding effects of other long-run
differences between neighborhoods (or
pairs of neighborhoods). I compare the
changes in commuting flows between pairs
of tracts where both received transit
stations and pairs of tracts where at least
one did not.
Figure 3 describes the comparisons
I make. Transit stations are built in both
location A and location B. This means that
both of the (directed) pairs AB and BA
receive transit. Locations C and D do not
receive transit. In total, 10 different pairs
do not receive transit: AC, AD, BC, BD,
CA, CB, CD, DA, DB, and DC. I compare
the average changes in the two pairs that
receive transit with the 10 pairs that do
not. Better yet, I can also purge the

changes at locations A and B that might be
caused by the transit station (as well as
any other changes that affect only A or B—
or C or D, for that matter).22 This isolates
the commuting effect, because the commuting flow between connected locations
is the only margin being shifted.
Still, one might worry that these places
were connected specifically because planners believed they were most in need of
transit connections. If that were so (and if
the planners were right), then changes
between newly linked neighborhoods
might have happened anyway. I limit the
control group of neighborhoods (that
is, the tracts that did not receive transit
linkages) in a couple of different ways
to ensure that this is not the case. Both
approaches rely on the historical antecedents of Los Angeles Metro Rail to select
control neighborhoods that are similar
to the neighborhoods that received transit
linkages. One approach identifies plausible
locations for receiving rail by examining
streetcar and interurban rail lines present
in the 1920s.23 Subway and light-rail lines
often follow these rights of way, and they
tend to align to allow lines to connect.
The other comparison uses a historical
subway plan from 1925. This plan is more
extensive than the subway that was built
and so shows many likely routes. Importantly, these routes would have connected
historic employment centers and so are
less likely to reflect current factors influencing travel demand.
I find strong evidence of a substantial
impact of Los Angeles Metro Rail on
commuting behavior. Pairs of neighborhoods connected by rail (that is, tracts
that both contain stations) experienced
a 15 percent increase in commuting
between them. Pairs of neighborhoods
immediately adjacent to (but not containing) stations saw a 10 percent increase
in commuting. More distant places did
not see a change (Figure 4). The effect
is strongest for pairs of tracts connected
by the same subway or light-rail line.
(People do not like changing trains, especially when driving is the alternative.)
Being close to a station is more important for the workplace location; people
seem more willing to walk a moderate
distance from home to a station than to
walk the same distance from a station
to work. Results are consistent across

A Ticket to Ride: Estimating the Benefits of Rail Transit
2020 Q2

FIGURE 3

Comparing Effects of Transit Stations

By measuring the commuting flow between connected locations, this model isolates the commuting effect.
Sites A and B
both receive new
transit stations,
but neither
Site C nor Site D
receives one.

Compare the changes in these transit-linked commuting pairs…
A→B, B→A
Site C

A

AB Transit Line

B

to these commuting pairs without transit links.
A→C, C→A
A→D, D→A
C

Site B

Site A

B→C, C→B
C

A

A

B
D

B→D, D→B

C→D, D→C

Site D

C

B

Note: Locations A and B receive transit stations; C and D do not.

D

D

different comparisons, adding strength to their interpretation as
a causal effect.
Although my main analysis focuses on the period between
1990 and 2000 (because the data in this period are of the highest
quality), commuting may have continued to adjust after the
year 2000 in response to the transit linkages built before 2000
that I study. I test for this, and find that commuting between
these locations continued to grow relative to other unconnected
neighborhoods by 6 to 11 percent over the next 15 years. This
delayed effect could be due to slow habituation: It takes people
and the built environment a while to adjust to the new transit
option. Alternatively, it could be due to the further growth of
the Los Angeles Metro Rail network after 2000.24 People value
transit more (and use it more) if it connects them to more places.
There is also evidence of a small reduction in automobile
congestion in areas served by rail transit. I compare changes in
travel times between pairs of neighborhoods that both lie near
a transit station or line with those that do not. Pairs of neighborhoods both within 2 kilometers of a transit line saw a 3 percent
reduction in travel time in the long run (though this finding is not
the most robust).25
Although I find evidence of commuting effects, I find little evidence of noncommuting effects. Residential locations did not,
on average, become nicer or worse off because of transit, and
workplaces did not become significantly more productive
because of transit. These results rely on comparisons between
a neighborhood that received a transit station and a neighborhood

FIGURE 4

The Impact of Los Angeles Metro Rail

+10%

+15%
Census tract

From 1990 to 2000,
tracts linked by a rail line
saw a 15% increase in
commuting. Adjacent
tracts saw a 10%
increase. More distant
tracts saw no change.

From 2000 to
2015, those
links grew
by 6–10%.

People care more about
working close to a station
than living close to one.

People prefer to not
change lines, especially if
the alternative is driving.

Source: Author’s calculations from Census Transportation Planning Project (CTPP)
data.

A Ticket to Ride: Estimating the Benefits of Rail Transit

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

5

that did not (rather than comparing a pair of neighborhoods
that received a transit linkage to a pair that did not), and so
depend more on identifying the correct control group for the
comparisons. Nonetheless, there is little evidence of an effect,
even when just comparing the neighborhoods most likely to
receive transit (as picked out by historic streetcar locations and
the 1925 subway plan).26
There is also little evidence of a barrier effect. Many transportation projects separate neighborhoods that lie along either
side of their routes, driving down the connections to nearby
locations.27 However, the first Los Angeles Metro Rail lines were
typically built along existing rail lines, underground, or in highway medians, and so they had little effect.

How Valuable Are These Commuting Effects?

To quantify the monetary value of these effects, I measure how
responsive people are to, first, the wages they receive in where
they choose to work and, second, the home prices they pay
in where they choose to live. The intuition works like this: If
a 10 percent increase in wages induces 18 percent more people
to work in a location (holding other workplace characteristics
constant), then an 18 percent increase in commuting to a location
is equivalent to a 10 percent increase in wages.28 In fact, this 18
percent value is what comes out of the analysis.
The hard part is ensuring that other changes in the workplace
or residential neighborhoods do not confound this measurement.
For example, if residential housing prices decline because local
school quality declines, the local residential population may
decrease. Or if employment at the ports goes down because of
less shipping due to trade conflicts, the remaining workers could
keep receiving the same wage. If I could not account for these
other factors, I might conclude that people like higher housing
prices and do not care about how much money they make.
Instead of directly trying to account for all the potential
factors that could influence these relationships, I try to find something that affects local wages but does not depend on other local
factors. I first calculate changes in how productive an industry is,
using wages and employment at the national level. I then
calculate how much these changes impact each workplace neighborhood based on how much employment in that neighborhood
was in each industry in 1990.29 Overcoming this challenge is
a key part of my 2019 working paper, and it (or a similar parameter) is key to translating observed changes to a dollar equivalent
in any modal choice or city structure approach.

General Equilibrium Effects

The final component of the analysis is to provide a way to account for spillovers across space. Changes in one neighborhood
can affect home prices in other neighborhoods throughout
the city because those changes can prompt all households to
reevaluate where they want to live, potentially leading some
households to move between neighborhoods. This type of general
equilibrium effect is important to consider whenever there are
large changes to a local economy.

6

Federal Reserve Bank of Philadelphia
Research Department

I lightly modify the flexible model of consumer location choice
used by Ahlfeldt and his coauthors and apply it to the Los Angeles
setting (using the various estimates discussed above). The primary
agents in the model are households, who must decide both
where to live and where to work. When deciding where to live,
they consider residential housing prices and how desirable the
neighborhood is. When deciding where to work, they look at
what the wages are and how desirable the workplace is. Finally,
they also care about how hard it is to travel between a pair of
residential and workplace locations.
When transit enters and changes how nice a commute is, or
when the characteristics of a neighborhood change, people move.
The model makes predictions about the average behavior of
people (that is, it tells us where the new population lives but
not necessarily who moves where), and so accounts for spillovers
in location choice.30 Housing prices and wages then adjust in
response to these changes in where people want to live and work.

Cost-Benefit Comparison and Speculation

Now all the pieces are in place. The commuting effects are
measured, there do not appear to be other workplace or residential effects, we have a way to translate these effects into
a money-equivalent amount, and we can account for general
equilibrium effects.
Combining these pieces, I estimate a benefit of between $109
million and $146 million annually by the year 2000. (The range
accounts for whether or not I include the benefits of reduced
congestion.) If I include the additional growth in commuting
from 2002 to 2015 between locations connected before 2000, the
total rises to an upper bound of $216 million annually by 2015.31
These are purely commuting benefits; they do not account for
other travel benefits (such as easing travel for noncommuting
trips) or environmental benefits. While these other benefits
might be substantial, rail transit is often promoted and judged
based on its effect on commuting.32
The total cost of the Los Angeles Metro Rail system built by
2000 was $8.7 billion.33 This can be converted to an annual cost
equivalent of between $218 million and $635 million per year.34
Annual operating subsidies were about $162 million. (These are
operating expenses less fare revenue for heavy and light rail.)
By summing these numbers, I find that the total annual equivalent cost of Los Angeles Metro Rail as of 2000 was between $380
million and $797 million per year.
The high-end estimates for benefits are therefore about $216
million annually, while the lower end of the costs are at least
$380 million annually (Figure 5). This means that there is
a sizable discrepancy between the cost of the system and the
benefits it delivers even after 25 years.
Why is this the case, and how generalizable is this conclusion?
There are two items to consider: How could the benefits have
been higher, and how could the costs have been lower.
Some of the features that make Los Angeles useful to study
mean that a suboptimal system was built. Instead of connecting
the densest residential and workplace populations, the subway and light-rail system initially connected many areas between

A Ticket to Ride: Estimating the Benefits of Rail Transit
2020 Q2

FIGURE 5

Costs and Benefits of Los Angeles Metro Rail
Despite growth in commuting, there's a sizable
discrepancy between costs and benefits.
Range, millions of dollars
Benefits

0

50

100

150

Costs
Without annual operating subsidies

200
250
Additional benefit
including same line
2002–2015 growth
in commuting

With annual operating subsidies

0

200

400

600

800

400

600

800

Benefits vs. Costs

0

200

Gap between costs and
benefits
Source: Author's calculations based on CTPP; cost numbers from
Los Angeles Metro’s Adopted Budgets and the U.S. Department of
Transportation's National Transit Database.

which there was not a lot of commuting. Restrictive
land-use regulations have likely inhibited further
development along these rail lines. At the same time,
many features of Los Angeles (a polycentric, automobile-oriented city without many high-density areas)
are common to other cities building rail transit.
Rail transit construction is generally expensive, and
some factors make Los Angeles particularly expensive to build in: Earthquake risk, coastal flooding,
and challenging geography all increase costs. What's
more, it appears that rail infrastructure typically
costs more in the U.S. than in other places.35 The
understanding of why costs are high is still limited.
Unfortunately, transit planners are often forced to
cut costs by building transit in places where people
do not really want to travel, creating a downward
spiral in usefulness.
By ridership numbers alone, Los Angeles Metro Rail
is actually performing better than the rail transit
systems of many other similar cities. In building
a relatively large network that begins to cover a geographically large cosmopolis, Los Angeles Metro
Rail could serve as the basis of a large transit system
integral to mobility in Los Angeles 100 years from now.
New York City in 2004 was much larger and denser
than it was in 1904, when its first subway line was completed. However, planners and politicians rarely get
the latitude or budget to plan on such timescales.

Notes
1 See Anas, Arnott, and Small (1998).

3 See Heblich, Redding, and Sturm (2018) and You (2017).

7 On average, and across cities worldwide, subways appear
to have an insignificant impact on overall population
growth, though they lead to more concentrated cities than
does comparable highway construction. See GonzalezNavarro and Turner (2018).

4 See Bailey et al. (2019).

8 See Black, Kolesnikova, and Taylor (2014).

5 Economists call the general phenomenon of increased
productivity in or near large collections of people or firms
agglomeration. See Chatman and Noland (2014).

9 Of course, automobiles are also valuable for increasing the
mobility of some people with disabilities.

2 See Severen (2019) for details of this hybrid method.

10 See Department of Transportation (2018).
6 See Duranton and Puga (2004) and Rosenthal and
Strange (2004).

A Ticket to Ride: Estimating the Benefits of Rail Transit

2020 Q2

11 See Davis, Williams, and Boundy (2016).

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12 See Duranton and Turner (2018).

(typically about one-third) of their income on housing. So if a 10 percent
reduction in housing prices in a neighborhood (holding other characteristics
of the neighborhood constant) induces 18% × (⅓) = 6% more people to
live in a neighborhood, then a 6 percent increase in commuting from that
location is equivalent to a 10 percent reduction in housing prices.

13 See Mangum (2017).
14 See Bowes and Ihlanfeldt (2001).
15 See Brinkman and Lin (2019).
16 See, for example, Billings (2011) and Chen and Whalley (2012).
17 See, for example, Allen and Arkolakis (2019) and Tsivanidis (2018).
18 Spatially detailed data on commuting behavior is available only for
1990 and 2000, and since 2002.
19 It was operated as three lines at the time; one line had two branches.
These are now operated as two lines.
20 There were also unique factors that arose during the planning and
construction of Los Angeles Metro Rail that help clearly differentiate the
direct effects of Los Angeles Metro Rail from other factors that could
influence neighborhood change. These factors argue for interpreting the
estimates described below as causal (rather than simply correlative).
See Severen (2019) for a description of an exploding clothing store and
more discussion.
21 Census tracts have on average 4,000 residents, though size can vary
quite a bit. There are about 2,400 census tracts in the area under
study, implying approximately 2,4002=5.76 million pairs of residentialworkplace connections.
22 This is accomplished by using neighborhood-by-year fixed effects.
23 Red Cars (the Pacific Electric Railroad’s Los Angeles streetcar system)
were a notable component of commuting in Los Angeles prior to WWII.
The last Red Car ran in 1961.
24 Neighborhoods that first became connected between 2002 and 2015
experienced a 9 to 13 percent increase.
25 This is between one-third and one-quarter the size of the short-run
effect Anderson found in his 2014 paper. He used the Los Angeles Metro
Rail labor strike of 2003 to provide very high-quality evidence that the
presence of rail service reduced congestion (as measured by vehicle
speed) along Los Angeles freeways by up to 12 percent. The difference
in findings is most likely due to the time frame: I study changes in
congestion after years have passed, while Anderson focused on travel
during an event that lasted about five weeks.
26 Because of data limitations, I only studied noncommuting outcomes
between 1990 and 2000 (rather than extending the analysis to 2015, as
I do for commuting).

29 Economists call these variables shift-share or Bartik instrumental
variables. Because of the particular setting and data in my 2019 working
paper, many critiques of this approach are not relevant here.
30 Economists often consider other externalities, sometimes called
spillovers, in these models. A typical externality is agglomeration.
Though I discuss this in my working paper, I do not discuss it here.
31 The increased commuting between 2002 and 2015 could be attributed
to either the slow adjustment of people to Los Angeles Metro Rail or the
growth of the network and increased service area after 2002. The
$216 million annual benefit attributes all the growth to slow adjustment
(and can therefore use the same cost basis as the $109–$146 million
annual benefit estimate).
32 For example, Nicolas Gendron-Carrier and his coauthors found that
subways decrease air pollution. Applying their estimates and methods to
Los Angeles suggests that Los Angeles Metro Rail may have up to an
additional $180 million in annual benefits (roughly equal to the commuting
benefit). Accounting for this brings total benefits within the lower end
of the cost range. However, it is not obvious that these benefits represent
a long-run gain, as decreased congestion from rail transit could eventually
induce more driving (and thus more pollution).
33 All dollar amounts have been inflation-adjusted to their 2015 equivalents. Figures are author’s calculations based on LACMTA fiscal year
budget filing reports.
34 The range captures the wide variety of assumptions used to value the
benefits of infrastructure projects.
35 There exists little detailed work comparing costs internationally, but
Alon Levy has created perhaps the most exhaustive dataset at his blog,
Pedestrian Observations. Brooks and Liscow (2019) showed that the
costs of other transportation infrastructure in the U.S. (specifically, highways) started to increase substantially in the late 1970s.

References
Ahlfeldt, Gabriel M., Stephen J. Redding, Daniel M. Sturm, and Nikolaus
Wolf. “The Economics of Density: Evidence from the Berlin Wall,”
Econometrica, 83:6 (2015), pp. 2127–2189, https://doi.org/10.3982/
ECTA10876.
Allen, Treb, and Costas Arkolakis. “The Welfare Effects of Transportation
Infrastructure Improvements,” NBER Working Paper w25487 (2019),
https://doi.org/10.3386/w25487.

27 See Brinkman and Lin (2019).
28 A similar approach works with housing prices, with one small
adjustment: We must account for the fact that people spend only part

8

Federal Reserve Bank of Philadelphia
Research Department

Anas, Alex, Richard Arnott, and Kenneth A. Small. “Urban Spatial Structure,”
Journal of Economic Literature, 36:3 (1998), pp. 1426–1464.

A Ticket to Ride: Estimating the Benefits of Rail Transit
2020 Q2

Anderson, Michael L. “Subways, Strikes, and Slowdowns: The Impacts of
Public Transit on Traffic Congestion,” American Economic Review, 104:9
(2014), pp. 2763–2796, https://doi.org/10.1257/aer.104.9.2763.

Gendron-Carrier, Nicolas, Marco Gonzalez-Navarro, Stefano Polloni, and
Matthew A. Turner. “Subways and Urban Air Pollution,” NBER Working
Paper w24183 (2018).

Bailey, Michael, Patrick Farrell, Theresa Kuchler, and Johannes Stroebel.
“Social Connectedness in Urban Areas,” NBER Working Paper w26029
(2019).

Gonzalez-Navarro, Marco, and Matthew A. Turner. “Subways and Urban
Growth: Evidence from Earth,” Journal of Urban Economics, 108 (2018):
pp. 85–106.

Billings, Stephen B. “Estimating the Value of a New Transit Option,”
Regional Science and Urban Economics, 41:6 (2011), pp. 525–536.

Heblich, Stephan, Stephen J. Redding, and Daniel M. Sturm. “The Making
of the Modern Metropolis: Evidence from London,” NBER Working Paper
w25047 (2018), https://doi.org/10.3386/w25047.

Black, Dan A., Natalia Kolesnikova, and Lowell J. Taylor. “Why Do so Few
Women Work in New York (and so Many in Minneapolis)? Labor Supply
of Married Women Across U.S. Cities,” Journal of Urban Economics, 79
(2014), pp. 59–71.
Bowes, David R., and Keith R. Ihlanfeldt. “Identifying the Impacts of Rail
Transit Stations on Residential Property Values,” Journal of Urban
Economics, 50:1 (2001), pp. 1–25.
Brinkman, Jeffrey C., and Jeffrey Lin. “Freeway Revolts! Highways,
Downtown Amenities, and Urban Growth,” Federal Reserve Bank of
Philadelphia Working paper 19-29 (2019).
Brooks, Leah, and Zachary D. Liscow. “Infrastructure Costs,” unpublished
manuscript (2019), https://dx.doi.org/10.2139/ssrn.3428675.
Chatman, Daniel G., and Robert B. Noland. “Transit Service, Physical
Agglomeration and Productivity in U.S. Metropolitan Areas,” Urban Studies,
51:5 (2014), pp. 917–937, https://doi.org/10.1177%2F0042098013494426.
Chen, Yihsu, and Alexander Whalley. “Green Infrastructure: The Effects of
Urban Rail Transit on Air Quality,” American Economic Journal: Economic
Policy, 4:1 (2012), pp. 58–97, https://doi.org/10.1257/pol.4.1.58.
Davis, Stacy C., Susan E. Williams, and Robert G. Boundy. Transportation
Energy Data Book: Edition 35, Knoxville, TN: Oak Ridge National
Laboratory, 2016.

Levy, Alon. Pedestrian Observations: Construction Costs, (2011). https://
pedestrianobservations.com/construction-costs/.
Mangum, Kyle. “The Role of Housing in Carbon Emissions,” Andrew
Young School of Policy Studies Research Paper Series 17-05 (2017),
https://dx.doi.org/10.2139/ssrn.2957749.
Monte, Ferdinando, Stephen J. Redding, and Esteban Rossi-Hansberg.
“Commuting, Migration, and Local Employment Elasticities,” NBER
Working Paper w21706 (2015).
Rosenthal, Stuart S., and William C. Strange. “Evidence on the Nature
and Sources of Agglomeration Economies.” In J. Vernon Henderson and
Jacques-François Thisse, eds., Handbook of Regional and Urban Economics,
vol. 4, San Diego: Elsevier, 2004, pp. 2119–2171.
Severen, Christopher. “Commuting, Labor, and Housing Market Effects of
Mass Transportation: Welfare and Identification,” Federal Reserve Bank
of Philadelphia Working Paper 18-14/R (2019).
Tsivanidis, Nick. “The Aggregate and Distributional Effects of Urban
Transit Infrastructure: Evidence from Bogotá’s TransMilenio,” unpublished
manuscript (2018).
You, Wei. “The Economics of Speed: The Electrification of the Streetcar
System and the Decline of Mom-and-Pop Stores in Boston, 1885–1905,”
unpublished manuscript (2017).

Department of Transportation, Bureau of Transportation Statistics. “TET
2018—Chapter 6—Household Spending on Transportation.” In Transportation Economic Trends, 2018, https://www.bts.gov/browse-statisticalproducts-and-data/transportation-economic-trends/tet-2018-chapter6-household.
Duranton, Gilles, and Diego Puga. “Micro-foundations of Urban
Agglomeration Economies.” In J. Vernon Henderson and Jacques-François
Thisse, eds., Handbook of Regional and Urban Economics, vol. 4, San Diego:
Elsevier, 2004, pp. 2063–2117.
Duranton, Gilles, and Matthew A. Turner. “Urban Growth and Transportation,” Review of Economic Studies, 79:4 (2012), pp. 1407–1440, https://
doi.org/10.1093/restud/rds010.
Duranton, Gilles, and Matthew A. Turner. “Urban Form and Driving:
Evidence from U.S. Cities,” Journal of Urban Economics, 108 (2018), pp.
170–191.
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Photo: FG Trade/iStock

Central Bank
Digital Currency

Daniel Sanches is an economic advisor and
economist at the Federal Reserve Bank
of Philadelphia. The views expressed in this
article are not necessarily those of the
Federal Reserve.

Is It a Good Idea?

A CBDC might make banking easier for you and me.
It might also change how banks operate.
BY DA N I E L SA N C H E S

T

hanks to recent technological advances, central banks can
issue a new type of money that travels through a network
of computers around the globe and is exchanged with
the click of a mouse or by using a mobile device. This central
bank digital currency (CBDC) could change how people make
payments and how financial firms operate. A CBDC is an efficient
payment instrument for both domestic and international transactions, but it might prompt households and firms to shift funds
away from bank deposits, increasing banks’ funding cost and
decreasing investment in the economy. This article examines
a CBDC’s potential benefits and trade-offs for society.

Types of Money

In modern economies, a central bank such as the Federal Reserve
issues two types of money: physical currency and reserves.
Physical currency is the paper notes, such as the dollar bills, that
most people use in their daily transactions. Reserves are a unit
of account denominated in the country’s own currency but issued

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Federal Reserve Bank of Philadelphia
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only to select financial institutions, which can hold the reserves
in accounts with the central bank.
Many central banks already issue reserves electronically. If
a financial institution has an account with a central bank, it can
sell assets (usually government bonds) to the central bank and
receive a credit in its central bank account for the value of that
transaction. Financial institutions and the central bank rarely
use physical currency to settle these large-denomination financial
transactions. Instead, they use computers. Thus, reserves are
typically a virtual currency issued by the central bank and used
for payments within a network of financial institutions. When a
financial institution needs to make a payment to another financial
institution, it usually transfers the amount electronically from its
reserves with the central bank to the other institution’s reserves.
Physical currency and reserves are both outside money—that is,
money created outside the private sector. Outside money can be
issued by a central bank, or it can take the form of an asset that
has an intrinsic value, such as gold or silver. When the central
bank buys government bonds from a financial institution, it pays

Central Bank Digital Currency: Is It a Good Idea?
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interest just like a money market mutual
fund account. In most advanced economies, financial institutions that are eligible
to hold an account with the central bank
already receive interest payments on their
balances. In other words, some financial
institutions have access to interest-bearing
outside money. A CBDC would allow the
central bank to pay interest to individuals
and nonfinancial firms, too.
Initially, the central bank would issue
a CBDC and stand ready to exchange it
one-for-one with physical currency, which
would be necessary to ensure that people
and firms feel comfortable with the new
payment instrument. Gradually, the central
bank would retire physical currency from
circulation until it is phased out.

CBDC as an Efficient Medium
of Exchange

Consumers typically earn little or no
interest on deposit accounts at commercial
banks and may pay considerable fees for
withdrawing cash from automated teller
machines. Merchants pay substantial
interchange fees for taking payments via
debit and credit cards. These fees reflect
both operational costs and profit margins
for card-issuing financial firms.
A central bank could offer a CBDC at no
cost to households and firms, which could
then earn interest on the balances they
hold at the central bank. Although the
central bank would bear the nonnegligible
costs of maintaining the digital transaction
records, it might find it worthwhile to
subsidize CBDC accounts, as they could
serve as a valuable public good.1

FIGURE 1

With a Printed Currency: Outside vs. Inside Money
OUTSIDE
MONEY

People’s use of
printed money
in daily life

$
Offline
Online

Central bank

INSIDE
MONEY

A

B

v$

Banks sell
bonds to the
central bank
to purchase
currency.

v$

Banks use a digital and largedenomination version of the
printed currency A for interbank
trades and B to settle inside
money payments, like cashed
checks, between different bank
accounts.

Bond

%

Banking network
But with a Digital Currency…
The central bank will slowly phase
out printed currency as it
introduces the new central bank
digital currency (cbdc).

$

Off
On lin
lin e
e

for them by increasing the reserve balances of that institution, which implies
that the supply of outside money in the
economy increases.
Inside money, such as bank deposits and
checkable mutual fund accounts, is created by financial firms within the private
sector. Unlike outside money, inside
money is necessarily a claim on some
private issuer. For instance, your checking
account with a commercial bank is an
asset for you but a liability for the bank. If
you decide to withdraw the balance in your
bank account, the bank must pay out
currency. If the bank makes good on its
promise to you, you no longer hold a claim
on the bank.
If you want to make a payment to someone who holds an account at a different
bank, you instruct your bank to transfer
the balance in your account to that person’s
account. This can be done by check, wire
transfer, or some other means. At the end
of the business day, your bank is required
to transfer reserves to the payee’s bank
for the value of that transaction. Alternatively, you can withdraw cash to make the
payment yourself. So, in a typical daily
transaction, the bank either pays currency
directly to its depositor or transfers
reserves to another financial institution.
In other words, the bank must reduce
its outside money holdings if a depositor
makes a payment to someone outside the
bank. Ricardo Lagos provides a useful
summary of the types of money available
to households and firms (Figure 1).
A CBDC is a new form of outside money
designed to eventually replace physical
currency. Because it is an electronic token,
any individual or firm holding CBDC can
make payments to all individuals and
firms within the CBDC computer network.
An important innovation associated with a
CBDC is that if the network is sufficiently
large, people can transfer balances without a commercial bank. For instance, you
could use your CBDC balance to pay for a
meal at your favorite restaurant or to order
a new refrigerator from an online retailer.
Your transaction is immediately settled
via a transfer of electronic outside money
to the seller.
Additionally, individuals or firms with
an account at the central bank can receive
interest payments proportional to their
balances, so a CBDC account can earn

C

D

C Individuals can also hold
interest-earning, cbdc
accounts with the central
bank. As more people
adopt the cbdc, D they can
use it to settle payments
from big-ticket purchases
to small-ticket expenses
directly without using
banks as intermediaries.

Central bank
Banks still sell bonds to the central bank
to purchase currency, but now it’s digital.
That same currency is now used for
high-denomination, interbank trading.

Bond

%

Central Bank Digital Currency: Is It a Good Idea?

2020 Q2

Federal Reserve Bank of Philadelphia
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If a CBDC paid an interest rate in line with other risk-free assets,
it could serve as an efficient payment instrument for all sorts
of transactions.2 A big reason why people hold bank deposits and
other checkable accounts at financial institutions (even though
they pay little or no interest) is because they make it easy for
households and firms to make payments. Although consumers
value these transaction services, they tend to economize on
currency and bank deposits in their portfolio because there is an
opportunity cost of holding money balances. That cost is the
difference between the interest rate on a risk-free asset and
the yield on money holdings. An efficient medium of exchange
would drive this differential to zero.
When interest rates rise, households and firms tend to transfer
some of their wealth from their noninterest-bearing checkable
accounts to risk-free assets. By paying an interest rate in line
with other risk-free assets in the economy, a CBDC would induce
people not to transfer money to those risk-free (but illiquid) assets.
In his classic 1969 article, Milton Friedman argued that in an
economy in which money did not receive a rate of interest, as is
now the case, people would hold too little wealth in the form of
money. By encouraging people to hold more money as a proportion of their portfolio, a CBDC could make everyone better off.3
One advantage of a CBDC is that its network can include
all households and firms in each country. By setting the interest
rate on a CBDC equal to the risk-free rate, the central bank
could then supply an efficient medium of exchange to all agents
in the economy.
Another benefit of a CBDC is that it can be a safe asset for
households and firms. The current banking system necessitates
an elaborate system of bank regulation to prevent bank failures
and bank runs. A government bankruptcy is less likely than
a banking crisis. Certainly, there is much less probability of a run
on a CBDC. As a result, a CBDC can promote financial stability in
the banking system.

Disintermediation in the Banking System

As we have seen, a CBDC is a new payment instrument that competes with all forms of inside money. If a central bank decides
to launch a CBDC with the previously described properties, some
households and firms will likely shift their funds from private
financial institutions to an account at the central bank, a process
economists call disintermediation.
To better understand disintermediation, suppose that a central
bank creates a CBDC overnight and offers to pay 4 percent per
annum interest on its account balances. Right now, commercial
banks in the U.S. offer a negligible, if not zero, interest rate on
most retail customers’ account balances. If commercial banks do
not change their interest rate strategy in response to the introduction of a CBDC, many people and firms will likely transfer their
balances to a CBDC account immediately. Because commercial
banks issue deposits to finance loans to households and firms, they
will have to contract their loan portfolio in response to a decline
in deposits, leading to disintermediation in the banking system.
The exact amount of this disintermediation depends on many
factors. For example, suppose that someone with a private-bank
account worth $2,000 decides to shift their balance to the newly

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Federal Reserve Bank of Philadelphia
Research Department

created CBDC. The private bank’s deposits—and its reserves with
the central bank—decline by $2,000. On the liability side of the
central bank’s balance sheet, reserves diminish by $2,000 and
the CBDC rises by the same amount.
Now suppose that the private bank initially had $20,000 worth
of assets, with $2,000 in reserves held in an account with the
central bank and $18,000 in loans to firms and households.
In other words, the private bank held 10 percent of its assets in
reserves. After one of its depositors transfers $2,000 to the CBDC,
the private bank ends up with no reserves at all. To return to
the desired portfolio composition, it would have to call in $1,800
worth of loans, holding everything else constant (Figure 2). But
this would happen only if the central bank does not issue new
units of the CBDC to buy assets from the private bank.
This example shows that the amount of loans generated from
within the private sector will likely contract upon the introduction
of a CBDC that pays a sufficiently attractive interest rate. If
households and firms shift their funds to a CBDC, and if nothing
else changes in the economy, intermediaries in the financial
system must contract their balance sheets, which is why the
creation of a CBDC can lead to a reduction in private-bank loans
to households and firms.
FIGURE 2

Before the Introduction of a Digital Currency
A customer makes
a deposit at Bank A…

$2,000

earning the customer
almost nothing…

~0%
interest

Reserves $2,000

Bank A

Disintermediation Process
so the customer moves his
$2,000 to the central bank
from Bank A…

The central bank creates
a new digital currency &
allows individuals to deposit at
the central bank directly…

$2,000
4%
interest

Bank A now has
both a smaller
balance sheet and
no reserves…

so it calls in loans to
create reserves…

leaving less to loan to
households & firms.

Loans to
households
and firms
$16,200
Total Assets $1,800

Central Bank Digital Currency: Is It a Good Idea?
2020 Q2

Loans to
households
while the
and firms
bank adds
$18,000
it to its
balance
Total Assets $20,000
sheet.

Under normal conditions, central banks, unlike
commercial banks and other private intermediaries,
do not provide intermediation services—that is, they
do not provide funding for private firms and households. Instead, the central bank typically just issues
currency or reserves to buy short-term government
securities. Although many central banks still hold
other types of assets on their balance sheets as a legacy
of the policy response to the 2007–2008 global financial crisis, most central banks say they will soon
return to normal operational procedures.
However, a central bank could invest the funds it
raises by issuing a CBDC in other assets, such as
corporate bonds and mortgage-backed securities. In
this case, disintermediation does not necessarily
reduce the supply of credit in the economy.
This discussion shows that the effects of a CBDC
on credit allocation, production, and consumption
can vary depending on how the central bank behaves
when launching a CBDC. Recent research examines
the effects of a CBDC when the central bank sticks
to its standard operational procedures, and when it
instead engages in private intermediation following
the creation of a CBDC.

CBDC Without Central Bank
Intermediation

Todd Keister4 and I have studied the effects of the
introduction of a CBDC in the context of a formal economic model. Throughout the analysis, we assume
that the central bank follows the standard procedure
of buying government bonds when it expands the
supply of CBDC and selling government bonds when
it contracts the supply. But we do not assume that
the central bank is necessarily backing all of the CBDC
supply with government bonds. For instance, the
central bank could finance some of the CBDC interest
payments by simply issuing more units of the CBDC.
Finally, we assume it doesn’t cost much for the central
bank to issue a CBDC.
We then consider all effects associated with the
introduction of a CBDC, including the reaction of
private banks. We find that although a CBDC promotes
efficient exchange, it crowds out private-bank deposits, raises private-banks’ funding cost, and decreases
investment. We show that despite these effects, a CBDC
raises the welfare of households in the economy under
certain conditions.
Once it introduces a CBDC, the central bank might
raise the interest rate paid on balances held at the
central bank to promote efficient exchange. As we
have seen, the private banking system currently offers
an interest rate on deposits lower than the interest rate
on risk-free assets, which leads to inefficient exchange.
Thus, in our analysis, the introduction of a CBDC is
necessarily associated with a higher interest rate on

CBDC balances than the interest rate on deposits prior
to the introduction of a CBDC, given that the central
bank’s goal is to create a CBDC that provides an efficient medium of exchange to households and firms. To
avoid losing funds to the central bank, private financial
firms will likely then raise the interest rate on their
deposits, too. A higher interest rate on deposits means
a higher funding cost for private banks, which will
likely charge more for their loans to borrowers.
Taking the costs of disintermediation into account,
we find that households will, nonetheless, often
benefit from the introduction of a CBDC. The benefits
of introducing an efficient medium of exchange more
than offset the increase in private banks’ funding cost
and associated decline in investment, resulting in
larger output for the whole economy.
This is true when investment frictions are relatively
small. Investment frictions take many forms. For
example, borrowers may know more than the private
bank about their future risks or actual revenues, so
banks bear added costs to ensure repayment of the
loan. Or, as in our model, private banks may be unable to capture a large enough share of the borrower’s
project payoffs.5 Whatever the cause, investment
frictions lead the private bank to demand a higher
interest rate as compensation than would be required
in the absence of frictions. Meanwhile, the bank will
refuse to make some loans that would be profitable in
the absence of investment frictions.
To maintain their spreads as their funding cost
rises, private banks raise the interest rate they charge
for loans, increasing the number of profitable projects they can no longer fund.6 These profitable
projects that are no longer funded—that is, projects
that would have been funded despite the investment
frictions—are the social cost of disintermediation.
For example, consider a local bank that accepts
deposits from households and then loans some of
that money to small businesses. Assume that all
borrowers are equally likely to default. Finally, assume
that the bank pays households 1 percent per annum
on their deposits and charges borrowers 5 percent
per annum on their loans. In this case, the bank spread
is 4 percent, which generates earnings to cover the
bank’s operational costs and create a profit margin
for the bank’s owners. If the bank’s funding cost
increases to 2 percent as a result of the introduction
of a CBDC that pays an interest rate of 2 percent per
annum, then the bank will end up charging borrowers
6 percent on their loans to maintain a bank spread
of 4 percent. Consequently, all projects that earned
a rate of return for the borrower of between 5 and 6
percent per annum are no longer profitable for the
borrower, so those borrowers will no longer apply for
these loans. Assuming that they have no other ready
source of funds, these projects will not get done.

Central Bank Digital Currency: Is It a Good Idea?

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We assume that investment frictions are relatively small, so we
expect to see a relatively small decline in the supply of loans
following an increase in the private bank’s funding cost. Because
we also calculate, upon the introduction of a CBDC, large benefits
from this more efficient medium of exchange, we conclude that
a CBDC benefits society. Although it can lead to disintermediation,
a CBDC is worthwhile.

CBDC with Central Bank Intermediation

In a recently published paper, Markus Brunnermeier and Dirk
Niepelt identified the conditions under which a shift of funds
from private-bank deposits to a CBDC does not change the aggregate portfolio of loans and securities for the whole economy. The
authors allow the bank to engage in private financial intermediation when issuing a CBDC. For instance, the central bank could
issue a CBDC to buy privately issued loans, such as mortgages
and commercial loans, from private financial institutions if doing
so is part of its intervention strategy.
Their analysis assumes that the central bank and private-sector
financial institutions are equally adept at identifying investment
opportunities and monitoring loans, which is unlikely in the real
world. They found that the introduction of a CBDC might not
crowd out the supply of loans to firms and households, which they
would use to finance private investment, if the central bank is
willing to engage in private financial intermediation.
Jesus Fernandez-Villaverde, Linda Schilling, Harald Uhlig, and
I have considered a framework in which the central bank,
unlike private financial institutions, cannot identify investment
opportunities and monitor loans. We believe this is a better
approximation of the real world, given that both investment and
commercial banks invest considerably in the selection, screening,
and monitoring of their borrowers, which requires both sophisticated software and highly qualified analysts.
Surprisingly, we found that even though the central bank can’t
identify all investment opportunities, it can introduce a CBDC
without disintermediation. If the central bank is willing to engage
in private financial intermediation when issuing a CBDC, it can
redeposit part of the funds raised from CBDC depositors with

14

Federal Reserve Bank of Philadelphia
Research Department

investment banks. These banks can identify profitable long-term
investment opportunities, which will provide the central bank
with revenue to finance the interest payments on a CBDC. The
result is that the supply of loans in the economy does not change
following the creation of a CBDC.
However, this does not account for the benefits of a socially
efficient medium of exchange. These analyses focused on the role
of banks as providers of intermediation services, and the conditions under which a CBDC, when combined with changes in the
central bank’s operational procedures, does not crowd out
private investment. We did not examine the role of banks as
providers of liquidity services through demand deposit accounts
that are used as a medium of exchange.
As we have seen, commercial banks pay negligible if any
interest on checking accounts, and high-yielding accounts offered
by investment banks are not always checkable. The Keister–
Sanches study, on the other hand, considered the benefits of
a CBDC designed to serve as an efficient medium of exchange,
even if it shifts the supply of credit because the central bank does
not engage in financial intermediation.

Conclusions

Central banks are investigating a CBDC’s benefits and trade-offs for
society. Although a CBDC can crowd out private-bank deposits
and increase private banks’ funding cost, it can also promote
efficient exchange and improve the allocation of resources in the
economy. Although the initial set of papers analyzing the effects
of a CBDC focused on some key elements, there are many other
aspects of the monetary system that require additional research,
such as the impact of a CBDC on the framework for the implementation of interest-rate policy for business-cycle adjustments.
As we have seen, discussions of the merits of a CBDC have led
economists to rethink the central bank’s role in the provision of
liquidity and intermediation services. The rise of new technologies
and competition from the private sector will likely result in
a fundamental change in central banking. Many scholars, including myself, think that this will be the greatest debate of our time
in the field of money and banking.

Central Bank Digital Currency: Is It a Good Idea?
2020 Q2

Notes
1 Michael Bordo and Andrew Levin have argued that a CBDC could be
implemented via accounts held directly at the central bank or via specially
designated accounts at supervised commercial banks, which would hold
the corresponding amount of funds in segregated reserve accounts at the
central bank.
2 A risk-free asset is a security that has a certain future return. For
instance, Treasury securities are considered a risk-free asset because the
U.S. government guarantees all future payments.
3 See my 2012 Business Review article for a detailed discussion of the
properties of efficient media of exchange.
4 Todd Keister is a professor of economics at Rutgers University. Previously,
he was an assistant vice president at the Federal Reserve Bank of New York.
5 In the contracting literature, some project payoffs may be nonpledgeable
for a number of reasons. For example, to keep a manager of a firm
properly motivated, the manager may need to receive a sufficiently high
compensation. But this means the firm can’t pledge the manager’s
future compensation to the bank.
6 The spread is the difference between how much interest a bank pays
to its depositors–also known as its funding cost–and how much interest
it collects from its borrowers.

References
Bordo, Michael, and Andrew Levin. “Central Bank Digital Currency and the
Future of Monetary Policy,” in Michael Bordo, John Cochrane, and Amit
Seru, eds., The Structural Foundations of Monetary Policy. Stanford, CA:
Hoover Institution Press, 2018, pp. 143–178.
Brunnermeier, Markus, and Dirk Niepelt. “On the Equivalence of Private
and Public Money,” Journal of Monetary Economics, 106 (2019), pp. 27–41.
Fernandez-Villaverde, Jesus, Daniel Sanches, Linda Schilling, and Harald
Uhlig. “Central Bank Digital Currency: Central Banking for All?” NBER
Working Paper 26753 (2020).
Friedman, Milton. The Optimum Quantity of Money and Other Essays.
Chicago: Aldine Publishing Company, 1969.
Keister, Todd, and Daniel Sanches. “Should Central Banks Issue Digital
Currency?” Federal Reserve Bank of Philadelphia Working Paper No.
19-26 (2019).
Lagos, Ricardo. “Inside and Outside Money,” in Steven N. Durlauf and
Lawrence E. Blume, eds., The New Palgrave Dictionary of Economics, 2nd
edition. London: Palgrave Macmillan, 2008.
Sanches, Daniel. “The Optimum Quantity of Money,” Federal Reserve
Bank of Philadelphia Business Review (Fourth Quarter 2012), pp. 1–15.

Central Bank Digital Currency: Is It a Good Idea?

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

15

Photo: DCorn/iStock

House Price Booms,
Then and Now
House prices rose rapidly in the run-up to the
crash of 2007, but not everywhere. Understanding
why can help us prepare for future recessions.

Burcu Eyigungor is an economic advisor
and economist at the Federal Reserve Bank
of Philadelphia. The views expressed in
this article are not necessarily those of the
Federal Reserve.

FIGURES 1 AND 2

The House Price Index Has Passed
Its Peak and Almost Equals It
When Deflated
U.S. FHFA All-Transactions House Price Index
500

BY B U RC U E Y I G U N G O R

H

300
200

ouse prices boomed in the early 2000s, but not everywhere. Many
places experienced only mild price increases.
Economists have two explanations for this diversity in the increase in
house prices across locations. One is that demand increased everywhere, but
prices increased more where supply could not easily expand. I call this
the aggregate demand view. In the second explanation, demand increased
more in densely settled areas where additional construction was difficult. As
more people wanted to live in those locations, aggregate house prices rose.
I call this the reallocation view.
I explore the evidence for both views. Although both mechanisms probably
contributed to this diversity of house prices during the boom, one was
likely dominant. Understanding which was dominant is especially important
now, as prices have risen again. The Federal Housing Finance Agency’s
(FHFA’s) all-transactions house price index has passed its previous peak, and,
when discounted by the GDP deflator, the index is very close to the previous
peak in real terms, too (Figures 1–2). The previous house price increase
was followed by a large bust leading to the Great Recession. Are we risking
another house price bust today?

16

Peak before the
Great Recession

400

Federal Reserve Bank of Philadelphia
Research Department

House Price Booms, Then and Now
2020 Q2

100
0

1975 Q1

Note: 1980=100.

2019 Q2
Sources: FHFA/Haver Analytics.

Deflated FHFA All-Transactions House Price Index
Peak before the
Great Recession

5
4
3
2
1
0

1975 Q1

2019 Q2

Note: House Price Index is deflated by GDP Implicit
Price Deflator. Grey bars represent recessions.
Sources: FHFA/Haver Analytics.

Two Views on the Aggregate House Price Boom

According to the aggregate demand view, the demand for housing
increased roughly similarly across locations, which led to the
house price boom.
An increased desire for homeownership may have directly
boosted demand. As more people want to buy homes, consumption of housing typically increases. Or something indirect may
have increased demand. Low interest rates or a relaxation of
borrowing constraints could have made homeownership more
accessible, leading to more demand for housing.
Regardless of cause, a demand shock would have spurred
households to want to consume more housing everywhere, but
prices would have increased even more where supply could
not expand easily (that is, where there was low supply elasticity).
In these locations, higher prices would have prevented locals
from consuming more housing and nonlocals from moving in.
Several economists embrace this view and have searched
for an aggregate shock that could have led to the aggregate
house price increase. Either their models do not differentiate by
geography,1 or they use different house supply constraints across
space to predict the differential house price growth.2 Either
way, these economists assume that places with more stringent
house supply restrictions were no more attractive to live in
during the boom.
But according to the reallocation view, a reallocation shock
made some locations more attractive than others. For this to
lead to higher aggregate house prices, people must have wanted
to move from less-dense areas (where housing could be created
cheaply) to areas where housing could not easily expand.3
Economists who embrace the reallocation view posit several
reasons why denser locations might have become more appealing. For example, the service sector, which has supplanted the
industrial sector in many parts of the country, benefits from
a density of population and requires less land than factories do.
FIGURE 3

House Prices Increased More in Some Bins

In 2000s, house price growth was concentrated in top two bins.
U.S. Fhfa all-transactions house price index, 1975–2017, 1975=100
HPI Increase, 1999–2007
Bin 1
Bin 2
Bin 3
Bin 4
0%
150%

1100
Bin 1

1000
900
800

Bin 2

700
600
Bin 3

500

Bin 4

400
300
200
100

1975 ‘80

1990

2000

2010

2017

Also, innovators benefit from proximity to other innovators.
Indeed, the rate of invention goes up with urban density.4
These views beget different policies. If the demand increase
for housing is similar across locations, federal policymakers may
want to diminish the magnitude of the boom-bust cycle through
regulation or monetary policy. Doing so would lower the cost
of a recession that might follow a large house price boom. But if
aggregate house prices rise because of reallocation, then federal
policymakers might not be able to stabilize house prices through
regulation or monetary policy. Instead, it would be up to local
governments to increase the housing supply and stabilize house
price increases by relaxing zoning and building restrictions.

Analyzing the Two Views

To analyze the relative importance of each view, I rank locations
according to their house price increase from 1999 to 2007. I split
locations into four separate bins, with each bin having a roughly
equal share of employment in 1999. Throughout the analysis, the
first (or top) bin saw the highest house price growth, the second
bin the second-highest house price growth, and so on.
There was a substantial house price increase during the early
2000s in the top two bins, but the increase was mild for the
bottom two bins (Figure 3). House prices in the first bin, which
had the highest house price increase during the early 2000s,
are once again booming, so maybe there is something different
about these locations—something that gives them more pronounced boom-bust cycles.5
House supply elasticity varies across locations, and this plays
a crucial role in both views. If aggregate demand increases,
people everywhere would like to consume more housing, but if
housing cannot expand in one location, house prices rise more
in that location. This dissuades locals
FIGURE 4
from consuming more housing or nonlocals from moving in. But if reallocation
More Barriers to
leads to higher aggregate prices, people
Development
should be moving into higher-priced
Two measures
locations where housing cannot expand
show it was harder
easily. In both views, prices increase more to expand housing
where housing cannot easily expand, but
in markets that saw
for different reasons.
highest increase in
Economists have two ways to assess
home prices.
how hard it is to expand housing. One is
Undevelopable Land
the Wharton Regulation Index (WRI),
Bin 1
which measures the regulatory hurBin 2
dles new development faces in different
Bin 3
locations. The other, the Saiz measure,
Bin 4
documents the share of undevelopable
0%
50%
land in the most populous 100 metropolWharton Regulation
itan areas.6 Figure 4 displays the average
Index
WRI and Saiz measure for all four bins.
Bin 1
(Each location is weighted by its employBin 2
ment in 1999.) Consistent with both views, Bin 3
Bin 4
constructing new housing is hardest in
0.0
0.4
0.8
the top two bins, which had the highest
price increases.
Source: Saiz (2010); University of Pennsylvania.

Source: FHFA.

House Price Booms, Then and Now
2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

17

Relative Housing Demand

FIGURE 5

One way to distinguish between the two views is by looking at the
correlation between house price growth and employment
growth during the house price boom of 1999–2007. If an aggregate
demand shock was dominant, places with higher house price
growth should have experienced lower employment growth—that
is, the correlation between house price growth and employment
growth across locations should have been negative. This is
because where supply cannot expand easily, house prices rise
more and employment growth suffers. But if the reallocation
forces are strong enough, then we would see that places with
higher house price growth also have higher employment growth
(that is, a positive correlation). In spite of higher house price
increases, the demand increase is so much stronger in these
locations that employment growth is higher as well.
To assess whether a location had strong employment growth,
it helps to know its initial employment. Employment in big
cities, which have less developable land, might not be able to
grow as fast as in small cities. Three percent employment growth
in a year might be very strong for a big city but unexceptional
for a small city.
This is why Figure 5 shows the logarithm of initial employment
in 1999 on the x-axis and employment growth between 1999 and
2007 on the y-axis. Blue dots denote locations in the top two bins
with the highest house price growth. Red dots denote locations
in the bottom two bins with the lowest house price growth. Each
dot represents the average of 20 locations. All the blue dots are
above the red dots, which means that, on average, places with
higher house price growth also had higher employment growth.
This indicates that reallocation was dominant during this period.7
Reallocation was strongly at play during the boom years, but
how does this compare to other periods? To find out, I look at how
employment has evolved across the different bins. Employment
grew faster in the first bin: From 1969, the first year data are
available, to 1995, employment in the first bin grew at an annual
rate of 2.9 percent; from 1995 to 2007, it grew at 2.4 percent.
In other words, we do not see an acceleration in the growth of
employment in the first bin during the period with higher
aggregate house price growth (Figure 6).
To clearly show the relative growth of the top bin, Figure 7
divides the average employment of the cities in each bin by the
average employment in the fourth bin. We see that the top bin
was composed of bigger cities overall, and it has grown faster
relative to the bottom bin during the sample period. Again, we
do not see an acceleration of this relative growth after 1995 (when
real aggregate house price growth increased).
My analysis of the data leaves us with a mixed conclusion. Yes,
there has been an ongoing reallocation across locations, and more
desirable locations in the first bin have had faster employment
and faster house price growth for a long time. But reallocation
does not seem to have accelerated during the early 2000s, so it is
at best an incomplete cause of that era’s large price boom. Given
that we are not able to settle the debate on what caused the steep
increase in house prices during the 2000s and why it is happening
again, we should keep an eye on risk factors that might lead
to excessive risk-taking, exacerbating the boom-bust episodes.

18

Federal Reserve Bank of Philadelphia
Research Department

Employment Grows Strongly in Top Two Bins

Logarithm of initial employment, 1999, on x-axis; employment growth,
1999–2007, on y-axis; each dot equals average of 20 locations
Bins 1 and 2
Bins 3 and 4

1.3
1.2
1.1
1.0
0.9

9

11

12

13

14

15

Source: FHFA and U.S. Bureau of Economic Analysis (BEA).

FIGURE 6

Employment Grows Most in First Bin…
Average employment in cities, thousands, 1969–2017
800
Bin 1

700
600
500
400
300

Bin 2

200

Bin 3
Bin 4

100
0

1969

1980

1990

2000

2010 2017

Source: BEA.

FIGURE 7

… Even When Normalized

Average employment in cities, thousands, 1969-2017, normalized by fourth bin
6

Bin 1

5
4
3
Bin 2

2

Bin 3
Bin 4

1
0

1969

1980

Source: BEA.

House Price Booms, Then and Now
2020 Q2

10

1990

2000

2010 2017

FIGURE 8

Higher-Risk Mortgages Spike After Rules Loosened
DTI ratio of 30-year fixed mortgages at origination, 2000–2018
50%

DTI≥40

40%
30%

DTI≥45

20%
10%
DTI≥50

0%

2000 Q1
2010 Q1
Source: Fannie Mae loan performance data.

2018 Q3

FIGURE 9

Riskier Loans Rise

After FHFA directed GSEs to increase maximum LTV, share of
riskier mortgages gradually increased.

Combined LTV ratio of 30-year fixed mortgages at origination, excl. refinance loans
50%
CLTV≥85

40%
30%

CLTV≥95

20%
10%
0%

2000 Q1
2010 Q1
Source: Fannie Mae loan performance data.

2018 Q3

F I G U R E 10

Only a Mild Increase in Construction Employment
Construction share of employment increased sharply during
the early 2000s, mildly since 2012.
House price growth and construction share in employment, 1969–2017
10%
8%
Bin 3
Bin 2
Bin 1
Bin 4

6%
4%
2%
0%

1969
Source: BEA.

1980

1990

2000

2010 2017

Risk Factors Facing the Economy

Three macroeconomic variables may have contributed to the
boom and bust of the 2000s: looser borrowing constraints,
a construction boom, and backward-looking credit scoring.
During (especially long-lasting) booms, risks may be forgotten
and creditors might relax borrowing constraints. When a recession
hits, creditors reinstate those constraints, exacerbating the bust.
To measure the effect of looser borrowing constraints, I focus
on loans acquired by government-sponsored enterprise (GSE)
Fannie Mae. Fannie Mae acquires only conforming mortgages.
To conform, the mortgage must not exceed the maximum
debt-service-to-income (DTI) ratio and the maximum loan-tovalue (LTV) ratio.
The loosening of the DTI constraint may have led to the housing
boom.8 Prior to 2008, GSEs Fannie Mae and Freddie Mac purchased mortgages with DTI ratios up to 65 percent. In early 2010,
when loose lending standards were blamed for the high mortgage default rates after the recession hit, the GSEs reduced the
DTI limit to 50 percent. Fannie Mae imposed additional credit
score requirements for mortgages with a DTI ratio between 45
and 50 percent.
Those constraints have recently been loosened. In April 2017
the FHFA eliminated additional requirements for mortgages up
to 50 percent DTI. The rule change had an immediate effect on
Fannie Mae mortgages: The percentage of 30-year fixed-rate
mortgages that originated with a DTI ratio greater than or equal
to 45 percent rose from 8.6 percent in the fourth quarter of 2016
to 27 percent in the third quarter of 2018 (Figure 8).
Meanwhile, in 2015, the FHFA directed the GSEs to increase the
maximum LTV from 95 percent to 97 percent. In response,
the share of 30-year fixed-rate mortgages with an LTV ratio greater
than 95 percent gradually increased to its highest level since
2000. Today these mortgages constitute around 25 percent of the
loans at origination (Figure 9). This gradual increase began in
2011, around the time that house prices began their rise.
Although these numbers indicate that there is increasing risk
in the market for conforming loans, loans with a DTI ratio
greater than 50 percent are far less common today than they were
before the Great Recession, and many of the highly risky nonconforming mortgages—such as balloon loans and no-interest
loans—no longer exist.
A second risk factor is a construction boom. Some economists
argue that the construction boom of the early 2000s created
an excess supply of housing, which led to the subsequent house
price crash.9
Whereas the construction share of employment increased
sharply during the early 2000s, the increase since 2012 has been
mild (Figure 10). This might be good news: If the economy slows
down, house prices may decline less than they did in the 2000s.
(The bad news: House prices may have been rising recently
because not enough housing was being built.)
Backward-looking credit scoring, when combined with a
swing in bankruptcy rates, is a third risk factor that may magnify
boom-bust cycles.
Figure 11 shows the bankruptcy rate for the different bins.
A 2005 change in bankruptcy law led to a large increase in
bankruptcy filings. (That is, many people rushed to file in 2005

House Price Booms, Then and Now
2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

19

before the change took effect.) Other than
this spike, the bankruptcy rate fell fast in
the first bin during the house price boom:
Before 1999, the first bin had the highest
bankruptcy rate; between 1999 and 2006,
it had the lowest.
F I G U R E 11

Bankruptcy Rate Fell Fast

First bin had highest bankruptcy rate
before 1999, lowest 1999–2006.
Bankruptcy rate, 1991–2017
1.0%
0.8%
0.6%
0.4%

Bin 3

0.2%

Bin 4
Bin 1

0.0%

Bin 2
1991

2017

Source: BEA.

There are three reasons why rising
house prices might lead to a drop in the
bankruptcy rate. First, households can
dip into their rising housing equity to pay
back their obligations. Second, households
don’t want to risk losing their homes—
and their rising equity—in bankruptcy. And
third, the housing boom might lead to
a stronger local employment market and
thus higher incomes for households.
Regardless of the cause of this lower
bankruptcy rate, backward-looking credit
scoring in the first bin would have led to
higher credit scores for those households
and possibly looser credit constraints.
During the recession that started in
2007, places that had previously seen the
largest increase in house prices and lowest
bankruptcy rate now had the largest
decline in house prices and the highest
bankruptcy rate. Although the households in the first bin would have had the
highest credit scores during the boom
(in backward-looking credit scoring), they

Notes

Conclusion

The second house price boom within two
decades shows that the 2000 boom was
not a one-off event. However, the current
cycle may be different. Although real
house prices are very close to their previous peak, construction growth is mild,
and we’re not seeing a return of the
riskiest type of mortgages, so the house
price decline in the next recession (which
may now be upon us) might be milder
than during the Great Recession. Nonetheless, discovering why house price cycles
have become more pronounced in the
last two decades should help us prevent a
large bust from following future booms.

References

1 See Favilukis et al. (2017), Garriga et al. (2019),
Greenwald (2018), He et al. (2015), and
Justiniano et al. (2019).
2 See Mian et al. (2013) and Mian and Sufi (2014).
3 See Gyourko et al. (2013), Davidoff (2016),
and Howard and Liebersohn (2019a, 2019b).
4 See Carlino et al. (2007).
5 The first bin’s most populous locations are
these metropolitan statistical areas: Los AngelesLong Beach-Anaheim (CA), WashingtonArlington-Alexandria (DC-VA-MD-WV), San
Francisco-Oakland-Hayward (CA), and MiamiFort Lauderdale-West Palm Beach (FL).

20

were in fact the riskiest borrowers when
future risks are taken into account. Rising
credit scores for these bankruptcy-prone
households may thus exacerbate boombust cycles by making it too easy for them
to get credit.

Federal Reserve Bank of Philadelphia
Research Department

6 See Saiz (2010).
7 Indeed, some of the cities in the first bin have
had quite large employment growth. For
example, between 1999 and 2007 employment
in Las Vegas-Henderson-Paradise (NV),
Phoenix-Mesa-Scottsdale (AZ), and RiversideSan Bernardino-Ontario (CA) grew more than
30 percent while housing supply expanded and
house prices rose.
8 See Greenwald (2018).
9 See McNulty (2009).

House Price Booms, Then and Now
2020 Q2

Carlino, Gerald, Satyajit Chatterjee, and Robert
Hunt. “Urban Density and the Rate of Invention,”
Journal of Urban Economics, 61:3 (2007),
pp. 389–419, https://doi.org/10.1016/j.jue.
2006.08.003.
Davidoff, Thomas. “Supply Constraints Are
Not Valid Instrumental Variables for Home
Prices Because They Are Correlated With Many
Demand Factors,” Critical Finance Review,
5:2 (2016), pp. 177–206,
http://dx.doi.org/10.1561/104.00000037.
Favilukis, Jack, Sydney C. Ludvigson, and Stijn
Van Nieuwerburgh. “The Macroeconomic Effects
of Housing Wealth, Housing Finance, and
Limited Risk Sharing in General Equilibrium,”

He, Chao, Randall Wright, and Yu Zhu. “Housing and Liquidity,” Review of
Economic Dynamics, 18:3 (2015), pp. 435-455, https://doi.org/10.1016/
j.red.2014.10.005.
Howard, Greg, and Carl Liebersohn. “What Explains U.S. House Prices?
Regional Income Divergence,” Society for Economic Dynamics 2019
Meeting Papers 1054 (2019a).
Howard, Greg, and Carl Liebersohn. “Why Is the Rent So Darn High?”
Charles A. Dice Center Working Paper No. 2018-17 (2019b), http://
dx.doi.org/10.2139/ssrn.3236189.
Justiniano, Alejandro, Giorgio E. Primiceri, and Andrea Tambalotti. “Credit
Supply and the Housing Boom,” Journal of Political Economy, 127:3 (2019),
pp. 1317–1350, https://doi.org/10.1086/701440.
Kaplan, Greg, Kurt Mitman, and Giovanni L. Violante. “The Housing
Boom and Bust: Model Meets Evidence,” Journal of Political Economy
(forthcoming).
Journal of Political Economy, 125:1 (2017), pp. 140–223, https://doi.org/
10.1086/689606.
Garriga, Carlos, Rodolfo Manuelli, and Adrian Peralta-Alva. “A Macroeconomic Model of Price Swings in the Housing Market,” American
Economic Review, 109:6 (2019), pp. 2036–2072, http://doi.org/10.1257/
aer.20140193.
Greenwald, Daniel. “The Mortgage Credit Channel of Macroeconomic
Transmission,” MIT Sloan Research Paper No. 5184-16 (2018), http://
dx.doi.org/10.2139/ssrn.2735491.
Gyourko, Joseph, Christopher Mayer, and Todd Sinai. “Superstar Cities,”
American Economic Journal: Economic Policy, 5:4 (2013), pp. 167–199,
http://doi.org/10.1257/pol.5.4.167.

McNulty, James. “The Long-Run Demand for Housing, the Housing Glut,
and Implications for the Financial Crisis,” Business Economics, 44:4 (2009),
pp. 206–215.
Mian, Atif, Kamalesh Rao, and Amir Sufi. “Household Balance Sheets,
Consumption, and the Economic Slump,” Quarterly Journal of Economics,
128:4 (2013), pp. 1687–1726, https://doi.org/10.1093/qje/qjt020.
Mian, Atif, and Amir Sufi. “What Explains the 2007–2009 Drop in
Employment?” Econometrica, 82:6 (2014), pp. 2197–2223, https://
doi.org/10.3982/ECTA10451.
Saiz, Albert. “The Geographic Determinants of Housing Supply,” Quarterly
Journal of Economics, 125:3 (2010), pp. 1253–1296, https://doi.org/10.1162/
qjec.2010.125.3.1253.

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2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

21

Research Update
These papers by Philadelphia Fed economists,
analysts, and visiting scholars represent
preliminary research that is being circulated
for discussion purposes.
From Incurred Loss to Current Expected Credit Loss (CECL):
A Forensic Analysis of the Allowance for Loan Losses in
Unconditionally Cancelable Credit Card Portfolios
The Current Expected Credit Loss (CECL) framework represents a new approach
for calculating the allowance for credit losses. Credit cards are the most common
form of revolving consumer credit and are likely to present conceptual and
modeling challenges during CECL implementation. We look back at nine years of
account-level credit card data, starting with 2008, over a time period encompassing
the bulk of the Great Recession as well as several years of economic recovery.
We analyze the performance of the CECL framework under plausible assumptions
about allocations of future payments to existing credit card loans, a key implementation element. Our analysis focuses on three major themes: defaults, balances,
and credit loss. Our analysis indicates that allowances are significantly impacted
by specific payment allocation assumptions as well as downturn economic
conditions. We also compare projected allowances with realized credit losses and
observe a significant divergence resulting from the revolving nature of credit card
portfolios. We extend our analysis across segments of the portfolio with different
risk profiles. Interestingly, less risky segments of the portfolio are proportionally
more impacted by specific payment assumptions and downturn economic
conditions. We also analyze the impact of macroeconomic forecast error and find
that it can be substantial and can be impacted by CECL implementation design
features. Overall, our findings suggest that the effect of the new allowance framework on a specific credit card portfolio will depend critically on its risk profile. Thus,
our findings should be interpreted qualitatively, rather than quantitatively. Finally,
the goal is to gain a better understanding of the sensitivity of allowances to
plausible variations in assumptions about the allocation of future payments
to present credit card loans. Thus, we do not offer specific best practice guidance.
Supersedes Working Paper 19-08.
Working Paper 20-09. José J. Canals-Cerdá, Federal Reserve Bank of Philadelphia
Supervision, Regulation, and Credit Department.

22

Federal Reserve Bank of Philadelphia
Research Department

Research Update
2020 Q2

The views expressed in these papers are
solely those of the authors and should not
be interpreted as reflecting the views of
the Federal Reserve Bank of Philadelphia
or Federal Reserve System.

Expanded GDP for Welfare Measurement
in the 21st Century
The information revolution currently underway has
changed the economy in ways that are hard to measure
using conventional GDP procedures. The information
available to consumers has increased dramatically as
a result of the Internet and its applications, and new
mobile communication devices have greatly increased
the speed and reach of its accessibility. An individual
now has an unprecedented amount of information on
which to base consumption choices, and the “free”
nature of the information provided means that the
resulting benefits largely bypass GDP and accrue directly
to consumers. This disconnect introduces a wedge
between the growth in real GDP and the growth in
consumer well-being, with the result that a slower rate
of growth of the former does not necessarily imply
a slower rate of the latter. The conceptual framework
for this analysis is developed in a previous paper (Hulten
and Nakamura [2018]), which extended the conventional
framework of GDP to include a separate technology
for consumer decisions based on Lancaster (1966b) and
developed the idea of expanded GDP (or EGDP). In this
paper, we use this framework to provide a detailed critique
of existing GDP- and price-measurement procedures
and summarize the existing evidence on the size of the
wedge between GDP and EGDP.
Working Paper 20-10. Charles Hulten, University of
Maryland, NBER, and Federal Reserve Bank of Philadelphia
Research Department Visiting Scholar; Leonard I.
Nakamura, Federal Reserve Bank of Philadelphia Research
Department Emeritus Economist.

Bargaining Shocks and Aggregate Fluctuations

Real Estate Taxes and Home Value:
Winners and Losers of TCJA

We argue that social and political risk causes significant aggregate
fluctuations by changing bargaining power. To that end, we document
significant changes in the capital share after large political events,
such as political realignments, modifications in collective bargaining
rules, or the end of dictatorships, in a sample of developed and
emerging economies. These policy changes are associated with significant fluctuations in output. Using a Bayesian proxy-VAR estimated
with U.S. data, we show how distribution shocks cause movements in
output and unemployment. To quantify the importance of these
political shocks for the U.S. as a whole, we extend an otherwise
standard neoclassical growth model. We model political shocks as
exogenous changes in the bargaining power of workers in a labor
market with search and matching. We calibrate the model to the U.S.
corporate nonfinancial business sector and we back out the evolution
of the bargaining power of workers over time using a new methodological approach, the partial filter. We show how the estimated
shocks agree with the historical narrative evidence. We document
that bargaining shocks account for 28 percent of aggregate fluctuations and have a welfare cost of 2.4 percent in consumption units.
Supersedes Working Paper 17-25.
Working Paper 20-11. Thorsten Drautzburg, Federal Reserve Bank
of Philadelphia Research Department; Jesús Fernández-Villaverde,
University of Pennsylvania and Federal Reserve Bank of Philadelphia
Research Department Visiting Scholar; Pablo Guerrón-Quintana,
Boston College and Federal Reserve Bank of Philadelphia Research
Department Visiting Scholar.

In this paper, we examine the impact of changes in the federal tax
treatment of local property taxes stemming from the implementation
of the Tax Cuts and Jobs Act (TCJA) in January 2018 on local housing
markets. Using county-level house price information and IRS tax data,
we find that capping the federal tax deduction of real estate taxes
at $10,000 has caused the growth rate of home values to decline
by an annualized 0.8 percentage point, or 15 percent, in areas where
real estate taxes as shares of taxable income exceeded the national
median. Additionally, these areas with a high real estate tax burden
suffered from reductions in market liquidity after the reform. Fewer
houses were transacted either in absolute numbers or as shares
of total listings, houses stayed on the market longer before being sold,
and more houses were listed with price cuts. Importantly, we find
that the housing market slowdown was accompanied by declines
in local construction employment growth as well as multifamily building
permits. Furthermore, on net more people moved out of these areas
after the reform. Finally, we show that the act has already had political
consequences. In the 2018 midterm Senate elections, more voters
voted for Democratic candidates in areas with high real estate tax
burden than for Republican candidates.
Working Paper 20-12. Wenli Li, Federal Reserve Bank of Philadelphia
Research Department; Edison G. Yu, Federal Reserve Bank of
Philadelphia Research Department.

Research Update

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

23

Piecewise-Linear Approximations and Filtering
for DSGE Models with Occasionally Binding
Constraints
We develop an algorithm to construct approximate decision rules
that are piecewise-linear and continuous for DSGE models with an
occasionally binding constraint. The functional form of the decision
rules allows us to derive a conditionally optimal particle filter (COPF) for
the evaluation of the likelihood function that exploits the structure
of the solution. We document the accuracy of the likelihood approximation and embed it into a particle Markov chain Monte Carlo
algorithm to conduct Bayesian estimation. Compared with a standard
bootstrap particle filter, the COPF significantly reduces the persistence
of the Markov chain, improves the accuracy of Monte Carlo approximations of posterior moments, and drastically speeds up computations.
We use the techniques to estimate a small-scale DSGE model to
assess the effects of the government spending portion of the American
Recovery and Reinvestment Act in 2009 when interest rates reached
the zero lower bound.
Working Paper 20-13. S. Borağan Aruoba, University of Maryland and
Federal Reserve Bank of Philadelphia Research Department Visiting
Scholar; Pablo Cuba-Borda, Board of Governors of the Federal
Reserve System; Kenji Higa-Flores, University of Maryland; Frank
Schorfheide, University of Pennsylvania, CEPR, NBER, PIER, and
Federal Reserve Bank of Philadelphia Research Department Visiting
Scholar; Sergio Villalvazo, University of Pennsylvania.

24

Federal Reserve Bank of Philadelphia
Research Department

Responding to COVID-19: A Note
We consider several epidemiological simulations of the COVID-19
pandemic using the textbook SIR model and discuss the basic
implications of these results for crafting an adequate response to the
ensuing economic crisis. Our simulations are meant to be illustrative
of the findings reported in the epidemiological literature using more
sophisticated models (e.g., Ferguson et al. [2020]). The key observation
we stress is that moderating the epidemiological response of social
distancing according to the models may come at a steep price of
extending the duration of the pandemic and hence the time these
measures need to stay in place to be effective. We caution against
ignoring this tradeoff as well as the fact that the timeline of the
pandemic remains uncertain at this point. Consistent with the prudent
advice of hoping for the best but preparing for the worst, we argue
that a comprehensive economic response should address the
question of how to safely “hibernate” the national economy for
a flexible time period. We provide a discussion of basic policy guidelines and highlight the key policy challenges.
Working Paper 20-14. Lukasz A. Drozd, Federal Reserve Bank of
Philadelphia Research Department; Marina M. Tavares, International
Monetary Fund.

Research Update
2020 Q2

Important Factors Determining Fintech Loan Default:
Evidence from the LendingClub Consumer Platform

Effects of Gentrification on Homeowners:
Evidence from a Natural Experiment

This study examines key default determinants of fintech loans, using
loan-level data from the LendingClub consumer platform during
2007–2018. We identify a robust set of contractual loan characteristics, borrower characteristics, and macroeconomic variables that are
important in determining default. We find an important role of
alternative data in determining loan default, even after controlling for
the obvious risk characteristics and the local economic factors. The
results are robust to different empirical approaches. We also find that
homeownership and occupation are important factors in determining
default. Lenders, however, are required to demonstrate that these
factors do not result in any unfair credit decisions. In addition, we find
that personal loans used for medical financing or small-business
financing are more risky than other personal loans, holding the same
characteristics of the borrowers. Government support through
various public-private programs could potentially make funding more
accessible to those in need of medical services and small businesses
without imposing excessive risk to small peer-to-peer (P2P) investors.

A major overhaul of the property tax system in 2013 in the city of
Philadelphia has generated significant variations in the amount of
property taxes across properties. This exogenous policy shock provides
a unique opportunity to identify the causal effects of gentrification,
which is often accompanied by increased property values, on homeowners’ tax payment behavior and residential mobility. The analysis,
based on a difference-in-differences framework, suggests that
gentrification leads to a higher risk of delinquency on homeowners’
tax bills on average, but there was no sign of a large-scale departure of
elderly or long-term homeowners in gentrifying neighborhoods
within five years after adoption of the new policy. While tax delinquencies were somewhat inflated by appeals for reassessments,
programs designed to provide tax relief for long-term homeowners
help mitigate the risk of tax delinquencies and displacement. Findings
from this study help researchers, policymakers, and practitioners
better understand the mechanisms through which gentrification may
impact long-term homeowners and the effectiveness of policies to
mitigate these tax burdens and displacement.

Working Paper 20-15. Christophe Croux, EDHEC Business School;
Julapa Jagtiani, Federal Reserve Bank of Philadelphia Supervision,
Regulation, and Credit Department; Tarunsai Korivi, Amazon.com;
Milos Vulanovic, EDHEC Business School.

Working Paper 20-16. Lei Ding, Federal Reserve Bank of Philadelphia
Community Development and Regional Outreach; Jackelyn Hwang,
Stanford University and Federal Reserve Bank of San Francisco
Community Development Visiting Scholar.

Research Update

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

25

Family Job Search and Wealth: The Added Worker
Effect Revisited
We propose and estimate a model of family job search and wealth
accumulation with data from the Survey of Income and Program Participation (SIPP). This data set reveals a very asymmetric labor market
for household members who share that their job finding is stimulated
by their partners’ job separation. We uncover a job search-theoretic
basis for this added worker effect, which occurs mainly during
economic downturns, but also by increased nonemployment transfers.
Thus, our analysis shows that the policy goal of increasing nonemployment transfers to support a worker’s job search is partially offset
by the spouse’s cross effect of decreased nonemployment and wages.
The added worker effect is robust to having more children and more
education in the household and does not just result as a composition of
heterogeneous individuals. We also show that the interdependency
between household members is understated if wealth and savings are
not considered. Finally, we show that gender equality in the labor
market not only improves women’s labor market performance, but it
also increases men’s accepted wages and nonemployment rates.
Supersedes Working Paper 16-34.

Extended Loan Terms and Auto Loan Default Risk
A salient feature of the $1.2 trillion auto-loan market is the extension
of loan maturity terms in recent years. Using a large, national sample of
auto loans from the entire auto market, we find that the default rates
on six- and seven-year loans are multiple times that of shorter fiveyear term loans. Most of the default risk difference is due to borrower
risks associated with longer-term loans, as those longer-term auto
borrowers are more credit and liquidity constrained. We also find
borrowers’ loan-term choice to be endogenous and that the endogeneity bias is substantial in conventional default model estimates.
To mitigate this risk, we separately estimate instrumental variable
regression and simultaneous equation models. Finally, we find evidence
of adverse selection in borrowers’ loan-term choices in the years when
six- and seven-year loans first became widely used, which dissipates
over time as lenders adjust to risks in the market.
Working Paper 20-18. Xudong An, Federal Reserve Bank of Philadelphia
Supervision, Regulation, and Credit Department; Larry Cordell,
Federal Reserve Bank of Philadelphia Risk Assessment, Data Analysis,
and Research (RADAR) Group; Sharon Tang, Federal Reserve Bank
of Philadelphia.

Working Paper 20-17. J. Ignacio García-Pérez, Universidad Pablo de
Olavide and FEDEA; Sílvio Rendon, Federal Reserve Bank of Philadelphia
Supervision, Regulation, and Credit Department.

26

Federal Reserve Bank of Philadelphia
Research Department

Research Update
2020 Q2

Central Bank Digital Currency: Central Banking for
All?

Partisanship and Fiscal Policy in Economic Unions:
Evidence from U.S. States

The introduction of a central bank digital currency (CBDC) allows the
central bank to engage in large-scale intermediation by competing
with private financial intermediaries for deposits. Yet, since a central
bank is not an investment expert, it cannot invest in long-term
projects itself, but relies on investment banks to do so. We derive an
equivalence result that shows that absent a banking panic, the set of
allocations achieved with private financial intermediation will also be
achieved with a CBDC. During a panic, however, we show that
the rigidity of the central bank’s contract with the investment banks
has the capacity to deter runs. Thus, the central bank is more stable
than the commercial banking sector. Depositors internalize this
feature ex ante, and the central bank arises as a deposit monopolist,
attracting all deposits away from the commercial banking sector. This
monopoly might endanger maturity transformation.

In economic unions the fiscal authority consists not of one, but of
many governments. We analyze whether partisanship of state-level
politicians affects federal policies, such as fiscal stimulus in the U.S.
Using data from close elections, we find partisan differences in the
marginal propensity to spend federal transfers: Republican governors
spend less. This partisan difference has tended to increase with
measures of polarization. We quantify the aggregate effects in a New
Keynesian model of Republican and Democratic states in a monetary
union: Lowering partisan differences to levels prevailing during
less polarized times increases the transfer multiplier by 0.30. The
observed changes in the share of Republican governors lead to variation in the multiplier of 0.20 in the model. Local projection methods
support this prediction.

Working Paper 20-19. Jesús Fernández-Villaverde, University of
Pennsylvania, NBER, CEPR and Federal Reserve Bank of Philadelphia
Research Department Visiting Scholar; Daniel Sanches, Federal
Reserve Bank of Philadelphia Research Department; Linda Schilling,
Ecole Polytechnique, CREST, and CEPR; Harald Uhlig, University of
Chicago, CEPR, and NBER.

Working Paper 20-20. Gerald Carlino, Federal Reserve Bank of
Philadelphia Research Department Emeritus Economist; Thorsten
Drautzburg, Federal Reserve Bank of Philadelphia Research
Department; Robert Inman, The Wharton School of the University of
Pennsylvania and Federal Reserve Bank of Philadelphia Research
Department Visiting Scholar; Nicholas Zarra, New York University
Stern School of Business.

Research Update

2020 Q2

Federal Reserve Bank of Philadelphia
Research Department

27

Q&A…
with Chris Severen, an
economist here at the
Philadelphia Fed.

Chris Severen
Chris grew up in rural Texas and Tennessee, and, after graduating from the
University of Texas at Austin with a degree
in Latin American studies and economics,
he worked at an energy efficiency consultancy. In 2017 he completed his PhD
at the University of California, Santa
Barbara, where he was advised by faculty
in both the Department of Economics and
the Bren School. His research interests
span urban, environmental, and development economics. You can learn more
about Chris at https://cseveren.github.io/.

28

Federal Reserve Bank of Philadelphia
Research Department

How did you become interested in
urban transportation?
I’ve always been interested in transportation systems. I mostly lived in small towns
until I went to college, and throughout
high school I’d drive 40 or more miles in
a day. That was just normal. Living in
Austin [for college] showed me the other
side of that. Austin is where I began to use
bikes and busses. It was easier when I was
a student, because the busses that served
central student corridors ran frequently.
Once I moved away from campus, I did that
less. In most cities, busses designed to
serve workers don’t function as well as
busses designed to serve students.

You’re currently working on a paper
about transportation in Mexico City.
What are you learning about Mexico
City’s transit system?
The private automobile is becoming an
increasingly common mode of transportation in middle-income cities like Mexico
City. When that happens, there’s lots of
problems associated with congestion, air
pollution, automobile safety. Mexico City
has tried to respond to these problems.
It’s invested massively in infrastructure,
building rail and bus rapid transit lines.
When you provide good transit, people like
it, and that’s true even if it’s a bus rather
than a train.

What makes transit “good”?
The most important things are headways
[waiting time between vehicle arrivals],
safety, and whether it goes where you
want it to go.

Why are you building a dataset of historical county-level vehicle registration
data in the U.S.?
Before World War II there was a lot of
regional variation in how and whether cars
were adopted. Los Angeles in the 1920s
had something like 2 to 3 times as many
cars per capita as Chicago. And this is in an
era where both cities had extensive transit
networks. It seems that this early adoption
[of automobiles in Los Angeles] paved
the way for what happened later. In the
absence of a public transit system or
a walkable city, cars represent access to
Q&A

2020 Q2

opportunity and mobility. So it’s interesting to understand how that early access
played out before we fully shifted to being
an automobile nation [after World War II].

Another paper you’re currently
working on is “Driving, Dropouts, and
Drive-throughs: Mobility Restrictions
and Teen Outcomes.” What have you
learned so far in this research?
We’re looking at how the adoption of
graduated driver’s license laws may limit
mobility for some teenagers. There might
be these substitute activities where, if
I now have to be in school [because I’m
no longer old enough to get a license],
maybe I won’t work, but maybe it was the
work that was really valuable to me. Preliminarily, we find that things go in the
direction that you would expect. People
are more likely to complete high school
and work less. But we’re trying to nail
down the exact degree of substitution.

What did you learn from your study
of the effect of climate change predictions on current land markets?
There is evidence that people are beginning
to associate specific shocks they are experiencing in their life with climate change.
Asset prices should reflect people's expectations about the future, not just the past,
so we wanted to test whether land, an
important asset, reflects forward-looking
beliefs and expectations regarding climate.
We found evidence that there is actually
a fair amount of weight put on future climate forecasts, and that weight had been
increasing over time, and it was stronger
where people believed in climate change.

If you were teaching urban economics
to college students, what would you
make the course’s key takeaway?
Cities are incredible engines of productivity
because people come together and have
new ideas and create things, but there are
costs to being so close together. Forward
progress comes from developing the
technologies and institutions that allow
people to benefit from exchanging ideas
and being in proximity without facing,
you know, the Bubonic Plague—or sitting
in traffic for two hours.

Data in Focus

GDPplus
The Philadelphia Fed collects, analyzes, and shares useful data
about the Third District and beyond. Here's one example.
GDPplus

Real GDP

Real GDI

10%

8%
6%
4%
2%
0%
−2%
−4%
−6%
−8%
−10%

Q1
2006

Q1
2007

Q1
2008

Q1
2009

Q1
2010

Q1
2011

Q1
2012

Note: Shaded areas indicate NBER recessions. The data measure the quarter-overquarter growth rate in continuously compounded annualized percentage points.

Economists often talk about total expenditures on goods and services produced
in the U.S. economy, also known as real
gross domestic product (GDP). But there's
another way to measure the economy.
Real gross domestic income (GDI)—which,
like GDP, is calculated by the Bureau
of Economic Analysis (BEA)—measures
payments such as salaries to the workers
who produce the goods and services.
From an accounting perspective, GDP
should always equal GDI, but the BEA
computes each measure using different
survey information. That means GDP
almost never equals GDI. Both measures
are useful (even though they often disagree), but sometimes we want one

Q1
2013

Q1
2014

Q1
2015

Q1
2016

Q1
2017

Q1
2018

Q1
2019

Q1
2020

Sources: Bureau of Economic Analysis (BEA) and NBER via Haver Analytics.
Federal Reserve Bank of Philadelphia.

estimate of the underlying and unobserved
U.S. economic activity driving the BEA's
official measures. In 2013, the Philadelphia
Fed's Real-Time Data Research Center
launched just such a measure. GDPplus
combines GDP with GDI to produce one,
easy-to-read measure of aggregate
economic activity. GDPplus is designed
to complement but not replace the BEA's
measures. As Assistant Director and
Assistant Vice President Tom Stark
explains, "We think analysts and policymakers will use GDPplus as well as
the BEA's estimates of GDP and GDI to
improve their understanding of the
dynamics of the U.S. economy."

Learn More
Online: philadelphiafed.org/researchand-data/real-time-center/gdpplus
E-mail:
Tom Stark: tom.stark@phil.frb.org
Patrick Doelp: patrick.doelp@phil.frb.org

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