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EconomicLetter

Vol. 2, No. 3
MARCH 2007­­

Insights from the

F e d e ra l R e s e rv e B an k o f Da l l a s

Obstacles to Measuring Global Output Gaps
by Mark A. Wynne and Genevieve R. Solomon

In the past, the focus

The Federal Open Market Committee routinely refers to resource

was largely on

utilization in its assessment of U.S. inflation risks. In the press release fol-

domestic slack.

lowing its January meeting, for example, the FOMC noted that although

Now, some analysts

core inflation had moderated, “the high level of resource utilization has the

contend the ongoing

potential to sustain inflation pressures.”

process of globalization

Other central banks frequently explain their monetary policy deci-

requires policymakers

sions in similar terms. In its February 2007 Inflation Report, for example,

to look at global
slack as well.

the Bank of England noted that “in the short to medium term, inflation is
influenced by the balance between the demand for private sector output
and the supply available to meet that demand. That balance reflects, in turn,
the degree of spare capacity within businesses and conditions in the labor
market.”

The production-function
approach arrives at
potential output by
determining the
economy’s available
stocks of labor and
capital, then combining
these endowments
with an estimate of
multifactor productivity.

These statements make it clear
that monetary policymakers pay close
attention to levels of resource use.
In the past, the focus was largely on
domestic slack. Now, some analysts
contend the ongoing process of globalization requires policymakers to
look at global slack as well.
A growing body of evidence suggests inflation in many countries is
less closely related than it once was
to domestic slack. There is also evidence — and this is more controversial — that domestic inflation may be
tied to global slack.
Calculating global production
capacity and slack presents challenges. This is true even when looking
at advanced industrial countries that
compile the data required to accomplish the task. But what happens
when nations don’t track the needed
numbers? What kind of problem does
that pose for policymakers, especially
when these nations are responsible for
a growing share of the world’s output?
Gauging Potential Output
The output gap — a key measure
of resource utilization — is the difference between the amount produced
in a given period and the economy’s
potential level of output.1 Positive
gaps — that is, output levels in excess
of potential—are usually associated
with increased price pressures. Negative gaps—output levels below potential—are usually associated with
decreased pressures.
Governments routinely report
actual production quarterly. To compute output gaps, however, we also
need measures of potential output.
Economists have taken two main
approaches to developing them.
The first relies on statistical techniques to estimate the trend growth
rate. The simplest estimate is a straight
line fitted to historical data. A drawback to this approach is the assumption that output will grow at a constant rate — an assumption that’s not
always warranted. The U.S. economy
grew faster in the two decades before

EconomicLetter 2

Fede ra l Reserve Bank of Dallas

1973 than it did in the two after, and
it expanded more rapidly over the
past decade than it did between the
early 1970s and early 1990s.
It’s possible to employ more
sophisticated approaches that allow
for varying trend rates of growth. While
relatively easy to implement, these
techniques are subject to a drawback
usually referred to as the end-point
problem. Estimates of potential output
derived from such measures tend to
be least reliable at the beginning and
end of sample periods. Errors in calculating output gaps of, say, 40 years
ago may be an issue for students of
economic history. But mismeasuring
today’s potential output can have serious implications if the estimates are
used in making policy decisions.
The main alternative to estimating
trend output is the production-function approach. It arrives at potential
output by determining the economy’s
available stocks of labor and capital,
then combining these endowments
with an estimate of multifactor productivity.
Start with labor. The total amount
of labor available for market production is determined by the size of the
working-age population, the labor
force participation rate, the employment rate and the number of hours
logged by the average worker.
The size of the working-age
population, usually defined as those
aged 15 – 64 or 25 – 64, changes slowly
and — more important — doesn’t vary
with the business cycle. The participation rate, unemployment rate and
average hours worked all tend to fluctuate with economic activity. They increase when the economy is expanding and decline when it’s contracting.
To measure potential labor input,
we need to calculate the trend levels
of these variables. When we do this
for the U.S., we find that the fundamentals determining how much labor
is available have varied over the past
half century or so.2
The labor force participation
rate — the fraction of the working-age

population that is either employed or
actively looking for work — fluctuated
around 59 percent through the 1950s
and mid-1960s. The rate climbed
steadily during the late 1960s and
through the 1970s and 1980s as more
women entered the labor force. It leveled off at around 67 percent during
the 1990s and 2000s when the influx
of women slowed (Chart 1A).
The unemployment rate exhibits
wide swings, which can be smoothed
with an estimate of the trend rate
(Chart 1B). A more useful measure
is the non-accelerating inflation rate
of unemployment (NAIRU), which
differs from the simple trend in that
it incorporates information about the  
relationship between inflation and
unemployment.
The NAIRU, as calculated by
the Organization for Economic
Cooperation and Development, rose in
the 1970s, possibly due to a productivity slowdown. It then ebbed in the
1980s and 1990s. The decline at the
end of the period may be related to
an acceleration in productivity.
The third component of the labor
input is average hours worked (Chart
1C ). From the mid-1960s through
early 1990s, average hours steadily
declined. They leveled off a bit above
34 hours a week in the 1990s, then
dropped around the turn of the century. Since then, the norm seems to be
a tad below 34 hours.
The capital stock is the second
element of the economy’s productive
capacity. The intensity of capital
stock use tends to vary over the business cycle. Companies add shifts
when the economy is expanding and
idle plants and equipment when it’s
contracting.
Measures of capacity utilization
try to capture these cyclical variations.
To gauge the economy’s potential output, however, we can use estimates of
the capital available at a given time.
Statisticians determine the capital stock
by tracking nations’ annual investment
in plants, equipment and buildings,
then adjusting for depreciation. The

Chart 1

U.S. Labor Force Changes over Time
A. Participation
Percent
69
67
Actual

65
63

Trend

61
59
57
55
1950 1954

1958

1962

1966

1970

1974

1978

1982

1986 1990

1994

1998

2002

2006

SOURCES: Haver Analytics; Bureau of Labor Statistics.

B. Unemployment
Percent
11

Actual

10
9
8

Trend

7
6

NAIRU

5
4
3
1970

1975

1980

1985

1990

1995

2000

2005

SOURCES: Haver Analytics; OECD Economic Outlook.

C. Average Weekly Hours Worked
Hours
40
Trend

38

Actual

36
34
32
30
1964

1968

1972

1976

1980

1984

1988

SOURCES: Haver Analytics; Bureau of Labor Statistics.

Fede ral Reserve B ank of Dallas

3 EconomicLetter

1992

1996

2000

2004

The big, emerging market
economies lack some
of the most fundamental
ingredients needed to
construct a measure of
resource utilization.

U.S. capital stock has grown steadily
over long periods.
Once we have estimates of available labor and capital, the remaining
part of the puzzle is productivity. The
key determinant of rising living standards is the increased output obtainable from available stocks of labor and
capital.
U.S. multifactor productivity has
been rising steadily (Chart 2). Annual
average growth has doubled from 0.7
percent in 1988 – 94 to 1.4 percent
since 1995.3
The production-function approach
yields reasonable potential output estimates for countries with timely, accurate measures of their labor and capital stocks. Analysts make assumptions
about the nature of technology to
combine labor, capital and productivity into a measure of potential output.
The Federal Reserve, Congressional
Budget Office, OECD and many other
organizations use this approach, with
variations, to estimate potential GDP
and the output gap. We concentrate

on the OECD’s estimates because
they’re available for a large number
of countries and based on a common
methodology.4
The OECD publishes output gap
estimates and forecasts for most of its
member countries, usually quarterly.
Output gaps for the U.S., G-7 nations
(U.S., Japan, Germany, U.K., France,
Italy and Canada) and OECD as a
whole tend to move together (Chart 3).
When output is below potential in the
U.S., it’s usually below potential in the
G-7 and the rest of the OECD as well.
These measures move in tandem
partly because the U.S. is included in
all three. But even a more detailed
look at individual countries would
show significant synchronization.
Many policymakers put considerable emphasis on output gaps in
their deliberations. We can see why
by looking at gap estimates for the
U.S., G-7 and OECD from 1970 to
2005 plotted against the change in
U.S. inflation over the subsequent
year (Chart 4 ). Inflation is measured

Chart 2

Multifactor Productivity Levels Climb Steadily
Log scale
2.06

2.04

2.02
Trend
Actual

2.00

1.98

1.96

1.94
1988

1990

1992

1994

SOURCES: Haver Analytics; Bureau of Labor Statistics.

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Fede ra l Reserve Bank of Dallas

1996

1998

2000

2002

2004

on a quarter-over-quarter basis as the
annualized change in the Personal
Consumption Expenditures deflator,
excluding food and energy.
Traditional Phillips curve reasoning would lead one to expect a positive correlation between the two sets
of data — and this is indeed the case.
Going Global?
Advanced industrial economies
have the data needed for computing
output gaps. These nations, however,
account for a shrinking share of global
output. In 1975, the OECD countries
generated 64 percent of global output,
measured on a purchasing power parity basis.5 By 2005, this number had
fallen to 53 percent.
Taking share away were the socalled BRICs—Brazil, Russia, India and
China — big, emerging market economies that lack some of the most fundamental ingredients needed to construct a measure of resource utilization.
Basic to measuring potential
output is, of course, actual production, and each of the BRICs produces
quarterly estimates of real GDP (Table
1). However, the accuracy of these
estimates is probably not on a par
with GDP numbers for the advanced
industrial countries.
Almost all governments conduct
a regular census, so annual data on
total population are usually available. Likewise, most nations report
the number of people employed and
unemployed, which together make up
the labor force.
However, China’s unemployment
rate only covers urban areas, making
it an inadequate measure of total labor
market slack. It’s generally believed
there are large numbers of underemployed — if not unemployed — workers
in rural China.
As for hours worked, only Brazil
reports an estimate, and it covers only
the manufacturing sector.
The next ingredient is capital.
As any visitor to China knows, the
country is in the midst of a construction boom. Yet, there are no official

Chart 3

Output Gaps Move in Sync
Percent
6
4

United States

G-7
2
0

OECD

–2
–4
–6
–8
1970

1975

1980

1985

1990

1995

2000

2005

SOURCE: OECD Economic Outlook.

Chart 4

U.S. Inflation Correlates with Output Gaps
Change in inflation (percent)
8

U.S. output gap
G-7 output gap
OECD output gap

6
4
2
0
–2
–4
–6
–8

–8

–6

–4

–2
Output gap (percent)

SOURCES: OECD Economic Outlook; Bureau of Economic Analysis.

Fede ral Reserve B ank of Dallas

5 EconomicLetter

0

2

4

Table 1

What the BRICs Measure
		
		
		
		

				
Labor input
Share of							
global GDP		
Capital			
Participation
Unemployment
(percent)
GDP
input
Population
rate
rate

China
13.5
Yes
No
Yes
Yes
							
India
6.0
Yes
				

Quality
questionable

Yes

Yes

Urban
areas only

No

Yes

No

Brazil
2.7
Yes
No
Yes
Yes
Yes
								
Russia
2.5
Yes
				

Quality
questionable

Yes

Yes

Average
hours worked

Yes

Manufacturing
only
No

SOURCES: Haver Analytics; Bloomberg; national statistical web sites.

Significant hurdles
must be cleared before
the traditional
production-function
approach to measuring
output gaps can be
extended to emerging
market economies.

estimates of China’s capital stock.
Attempts have been made to produce
unofficial estimates of China’s capital
stock — the seminal contribution being
made by Gregory C. Chow in 1993—
but they’re sometimes based on heroic
assumptions.6
Nor does Brazil report official
estimates of its capital stock, although
unofficial estimates have been made.7
There are official estimates for Russia,
but most analysts consider the quality poor.8 India also produces official
estimates, but they’re based on spotty
information about how long capital
is used before being discarded, and
they’re probably not on a par with
similar data for advanced countries.9
Some may find the absence or
poor quality of official capital stock
numbers surprising, given that all four
countries report investment, a key
input for such an estimate.
In economies undergoing rapid
structural change, however, the
standard assumptions used to total
annual investment flows into an
estimate of the capital stock — such
as stable or constant depreciation
rates — may be untenable. After all,
the essence of economic reform is
the wholesale scrapping of outdated

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Fede ra l Reserve Bank of Dallas

plants and equipment that are still
usable but no longer economically
productive and their replacement by
newer, more efficient structures and
machines.
For countries like China and
Russia, it’s difficult to assign an accurate value to plant and equipment in
current or former state-owned sectors.
For countries like Brazil and India,
with large informal sectors, much
investment may go uncounted.
Significant hurdles must be
cleared before the traditional production-function approach to measuring output gaps can be extended to
emerging market economies. These
hurdles have an interesting parallel
in the U.S. We have abundant statistics on the agriculture and manufacturing sectors, but scant information
on the increasingly important, but
difficult to measure, service sector. On
the international level, there is abundant and timely information on highly
developed economies, but relatively
few hard statistics on the increasingly
important emerging market economies.
Reliability an Issue
Even if we had data to construct
output gap measures for the BRICs,

the resulting estimates would probably
be subject to considerable uncertainty.
OECD nations can afford to devote far more resources to collecting
economic statistics than the emerging
economies. But comparing the OECD’s
most recent output gaps with estimates
of various vintages shows that revisions — often large ones — are common
(Chart 5).10 Today’s data show OECD
output was about 1 percent below
potential in 1997. In June 2003, however, output was estimated as being at
potential in 1997, with no gap at all.
A second reason for questioning
the usefulness of constructing global
output gap measures is the weakening of the correlation between existing measures and U.S. inflation. We
looked at two different break points,
one corresponding to Eastern Europe
and the Soviet Union’s opening in
1990, the other to the onset of the
IT revolution in 1995. Regardless of
where we split the sample, a striking decline occurs in the correlation
between the measured output gaps
and subsequent inflation (Table 2).
It’s well known that for both the
U.S. and the other OECD countries,
the relationship between domestic
slack and inflation has weakened,
although the reasons for this aren’t
well understood. Globalization is one
possible explanation. Better monetary
policy is another.
If central bankers are to use a
broader, global measure of the output gap in their deliberations, data
deficiencies will present a major challenge. And even if the data obstacle is
overcome, interpreting the global output gap in real time will be as much
art as science.
Wynne is a senior economist and vice president and Solomon an economic analyst in the
Research Department of the Federal Reserve Bank
of Dallas.

Chart 5

Revisions Plague Estimates of OECD Output Gap
Percent
2.5
2
Range of
previous estimates

1.5

Estimate as of
December 2006

1
.5
0
–.5
–1
–1.5
–2
–2.5
1990

1992

1994

1996

1998

2000

2002

SOURCE: OECD Economic Outlook.

Table 2

Correlation Between Output Gaps
and Subsequent U.S. Inflation

1970–2005
1970–1989
1990–2005
1970–1994
1995–2005

Correlation
with
U.S. gap

Correlation
with
G-7 gap

Correlation
with
OECD gap

.47
.53
.07
.50
.13

.42
.51
–.15
.45
.05

.23
.36
–.13
.26
.06

NOTES: The G-7 correlation for the 1970 – 89 period is for 1971–89; the OECD correlation
is for 1979–89. Data are quarterly.
SOURCES: OECD Economic Outlook; Bureau of Economic Analysis.

Fede ral Reserve B ank of Dallas

7 EconomicLetter

2004

EconomicLetter
Notes
1

5

This is a very traditional definition. The modern

Czech Republic, Slovak Republic and Poland

are excluded because GDP data adjusted for

literature on the theory of monetary policy (as

purchasing power parity do not go back to 1975

exemplified by Michael Woodford’s Interest and

for these countries.

Prices) defines output gaps somewhat differ-

6

ently, as the deviation of actual output from what

China,” by Gregory C. Chow, Quarterly Journal of

it would be in a frictionless world.

Economics, vol. 108, August 1993, pp. 809–42.

2

In each case, the trend value is estimated

7

“Capital Formation and Economic Growth in

See, for example, “Capital Accumulation in

using the Hodrick–Prescott filter with smoothing

Latin America: A Six Country Comparison for

parameter equal to 1600.

1950–89,” by André A. Hofman, Review of

3

A mathematical formula shows how these ele-

Income and Wealth, vol. 38, December 1992, pp.

ments are combined to arrive at an estimate of

365 – 401, and “Estimativa do estoque de rique-

potential GDP:

za tangível no Brasil, 1950 – 1998,” by Adalmir

GDP = (A × POP × LFPR ×
(1− NAIRU ) × HRS )α (K )1−α ,
where GDP denotes potential GDP, A is trend
multifactor productivity, POP the working-age
population (usually those aged 15 – 64), LFPR
the trend rate of labor force participation,

A. Marquetti, Nova Economia, vol. 10, December
2000, pp. 11 – 37.
8

See, for example, “National Wealth Estimation

in the USSR and the Russian Federation,” by
Leonid I. Nesterov, Europe–Asia Studies, vol. 49,
December 1997, pp. 1471 – 84, or “Measuring
the Capital Stock in Russia: An Unobserved

NAIRU the non-accelerating inflation rate of

Component Model,” by Stephen G. Hall and

unemployment, HRS the trend level of annual
hours worked per employee, K the capital stock

35, issue 4, 2002, pp. 365 – 70.

and a the average share of labor income in
national income. The output gap is defined as
Gap = GDP − GDP .
4

Details of the OECD’s approach are given

in “New OECD Methods for Supply-Side and
Medium-Term Assessments: A Capital Services
Approach,” by Pierre-Olivier Beffy, Patrice
Ollivaud, Pete Richardson and Franck Sédillot,
OECD Economics Department Working Paper no.
482, July 2006.

is published monthly
by the Federal Reserve Bank of Dallas. The views
expressed are those of the authors and should not be
attributed to the Federal Reserve Bank of Dallas or the
Federal Reserve System.
Articles may be reprinted on the condition that
the source is credited and a copy is provided to the
Research Department of the Federal Reserve Bank of
Dallas.
Economic Letter is available free of charge
by writing the Public Affairs Department, Federal
Reserve Bank of Dallas, P.O. Box 655906, Dallas, TX
75265-5906; by fax at 214-922-5268; or by telephone
at 214-922-5254. This publication is available on the
Dallas Fed web site, www.dallasfed.org.

Olivier Basdevant, Economics of Planning, vol.
9

See “National Accounts Statistics Sources

and Methods, 1989,” from the Indian Ministry
of Statistics and Programme Implementation,
Central Statistical Organization, http://mospi.nic.
in/nas_snm.htm.
10

The December 2006 issue of Economic Letter

addresses how revisions to economic statistics
can complicate the job of economic policymakers. Available at www.dallasfed.org/research/
eclett/2006/el0612.html.

Richard W. Fisher
President and Chief Executive Officer
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W. Michael Cox
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Senior Vice President, Banking Supervision
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Editor
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