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ESSAYS ON ISSUES

THE FEDERAL RESERVE BANK
OF CHICAGO

OCTOBER 1998
NUMBER 134

Chicago Fed Letter
A new paradigm for the
U.S. economy?
It is virtually impossible these days to
avoid articles in the popular press that
hail the dawn of a new paradigm in
which the old truths about the U.S.
economy no longer hold. These stories are fueled by a robust economic
expansion that seems to have no end
in sight. At the core of the new paradigm is the belief that the U.S. has
experienced a structural change that
has raised its trend growth rate, so that
the economy can now expand at rates
much greater than in the past without
igniting higher levels of price inflation.1 Many economists have argued
against the new paradigm by pointing
to temporary or cyclical events that
have a favorable impact, but have not
altered the trend growth rate of U.S.
output. At the heart of this debate is
the age old problem of decomposing
movements in output into trend and
cyclical components. This Chicago Fed
Letter reviews economists’ long-established ways of extracting the trend and
cyclical components from economic
time series and applies some newer
techniques to recent movements in
U.S. output.
What differentiates the trend
and cycle?
Trend output defines the level of production at which the economy’s labor
and capital inputs are being used at
their long-run sustainable levels of
effort or capacity. Trend output can
increase as a result of either a one-time
innovation that raises the level of production but leaves the growth rate
unchanged (known as a level shift) or
an innovation that changes the underlying growth rate. Growth theory has
devoted most of its attention to differentiating between factors that lead to

level shifts of the trend and those
that influence the trend growth rate.
Some theorists argue that the trend
growth rate is an exogenous constant,
determined by technological factors
that cannot be influenced by private
agents or government.2 Others argue
that the trend growth rate is endogenous,
that it can be influenced by the actions
of private agents or government.3 Advocates of the new paradigm typically
argue that globalization and recent
innovations in information technology
have permanently raised the trend
growth rate of the economy, which
suggests that it may be endogenous.
Prior to settling these theoretical issues
the actual trend must be measured.
In doing so we must also identify the
cyclical component of output. The
cyclical component captures temporary
or unsustainable short-run movements
in output around the trend. Economic
models suggest that these fluctuations
lower the well-being of consumers, for
example, through lay-offs or price
inflation, so it is not surprising that
cyclical output movements receive a
lot of attention from economists. The
theoretical and empirical analysis of
cyclical components, known as business
cycle theory, is one of the more contentious fields of economics. There are
many competing theories of the business cycle and, despite the old age of
this debate, there is little consensus
on the causes of cyclical fluctuations.4
Accordingly, theory offers little guide
to the appropriate way to measure
trend and cyclical components of
economic time series. The only thing
theory imposes on empirical methods
is that trend and cyclical terms be independent. This is an outgrowth of the
heretofore independent study of
growth and the business cycle; independence implying that the trend
and cycle are unrelated.

Independent trend/cycle
decomposition
Until recently output was generally
thought to have a deterministic trend.
In other words, economists assumed
that trend output grew at a constant
long-run rate. The late 1970s saw the
development of statistical techniques
aimed at identifying whether a series
had a deterministic or stochastic trend.
In a time series with a stochastic trend,
shocks to production have a permanent
effect on the level of output, while with
a deterministic trend, shocks have
no long-run effect on the level of output. Nelson and Plosser discovered
that many time series have stochastic
trends.5 This observation spawned a
popular approach to modeling time
series with stochastic trends known as
the Beveridge and Nelson decomposition.6 A weakness of their approach
is that it does not allow for the independent trend/cycle decomposition
sought by growth and business cycle
researchers. By the mid-1980s economists overcame this shortcoming by
employing spectral and unobserved component techniques to isolate independent trend and cyclical components.
Spectral techniques
Despite the wide-ranging views on the
causes of cyclical movements, economists have reached a consensus on the
definition of the cyclical component
of the data. Fluctuations in the data at
the so-called business cycle frequencies
of between 18 months and eight years
are considered cyclical movements.
While long-run fluctuations occurring
at frequencies greater than eight years
are the trend component, very shortrun movements occurring at frequencies
of less than 18 months are considered
an irregular component or noise. The
most convenient way to extract these

components is by employing spectral
techniques. The first step is to transform the data from the more usual time
domain (i.e., ordering data sequentially by months, quarters, or years) to
the frequency domain (i.e., ordering
data by how often it occurs)—low frequencies refer to smoother long-run
movements, while high frequencies
refer to more volatile short-run movements. The next step is to eliminate
frequencies we are not interested in.
This is done through low-pass filters
that eliminate high frequencies, highpass filters that eliminate low frequencies, and band-pass filters that eliminate
high and low frequencies. The trend,
cycle, and noise components are extracted by appropriately calibrated
low-, band-, and high-pass filters,
respectively.

An early example of trend/cycle
decomposition using spectral techniques was the Hodrick and Prescott
filter.7 They developed an approximate
high-pass filter to isolate data at frequencies less than eight years and
treated this is as the cyclical component. Baxter and King improved upon
this approach by developing an approximate band-pass filter (BP) to isolate
the business frequencies of 18 months
to eight years, thus eliminating the
noise present in the Hodrick-Prescott
cyclical term (these competing methods generate virtually identical trend
components when applied to seasonally adjusted quarterly data).8
Unobserved component techniques
Another group of economists led by
Watson took a completely different

1. Trend component of GDP, BP method

approach to independent trend/cycle
decomposition by applying unobserved
component techniques (UC).9 In contrast to spectral methods, UC methods
require strong assumptions about the
data generating process. Watson modeled the trend of the log of output as
a random walk with drift and the independent cyclical component as a secondorder autoregression. Watson’s approach
explicitly assumes that the current log
of output depends on its most recent
past observation plus some random
component and a constant term. The
constant, typically called drift, measures
the underlying trend growth rate. That
is, in the absence of random fluctuations trend output grows at a rate equal
to the drift term. In contrast, positive
random fluctuations lead to trend
growth in excess of the drift, while
negative random fluctuations cause

2. Trend component of GDP, UC method

log level

log level

9.1

9.1

BP trend
GDP

UC trend
GDP

8.6

8.6

8.1

8.1

7.6

7.6

1962

’66

’70

’74

’78

’82

’86

’90

’94

’98

3. Cycle component of GDP

1962

’66

’70

’74

’78

’82

’86

’90

’94

’98

4. Trend growth rate of GDP

percent deviation from trend

percent, annual rate
14

5.0

BP trend
UC trend
UC underlying
trend

BP cycle
UC cycle
2.5
7
0.0
0
-2.5

-5.0
1962

-7
’66

’70

’74

’78

’82

’86

’90

’94

’98

1962

’66

Notes: BP indicates the band-pass filter method. UC indicates the unobserved component method. Data cover the period
of 1962:Q1 to 1998:Q1. Shaded areas indicate recessions.
Source: Authors’ calculations based upon data from the U.S. Department of Commerce, Bureau of Economic Analysis,
National Income and Product Accounts, 1962–98.

’70

’74

’78

’82

’86

’90

’94

’98

the trend to grow by less than the drift.
We build on Watson’s work by introducing a time-varying drift term to his
model.10 This allows the trend growth
rate to change over time. (In our model the time-varying drift is modeled as
a random walk. This model is supported by a statistically significant estimate
of the variance of innovations driving
fluctuations in the growth term—a
constant drift term would require that
the innovation variance be zero.)
Empirical results
Figures 1 and 2 plot the log of real
gross domestic product (GDP) and
the implied trend from 1962:Q1 to
1998:Q1 using both the UC and the BP
methods.11 The BP trend is smoother
than the UC trend. In contrast, the UC
cycle plotted in figure 3 is smoother
than the BP cycle. Note that common
turning points in the UC and BP cycle
match business cycle peak-to-trough
dates measured by the National Bureau
of Economic Research. According to
the UC measure, the U.S. economy has
been operating below its trend, i.e., below its long-run sustainable capacity,
over the last two years. Overall these
competing methods generate very
similar cyclical components, which
suggests that the UC cycle is consistent
with data drawn from business cycle frequencies of 18 months to eight years.
The advantage of the UC approach is
that it generates an estimate of the
underlying growth rate of the trend,
which differs from the growth rate of
the trend itself since the trend is subject to shocks that may permanently
change its level while not changing its
growth rate. Figure 4 plots the growth
rate of the UC trend against the UC
underlying trend growth rate and the
BP trend growth rate. The BP trend
growth rate and the UC underlying
trend growth rate are considerably
smoother than the UC trend growth
rate. While the BP and UC underlying
trend growth rates have been increasing over the 1990s, they have been
doing so very slowly and are not any
greater than they were in the 1980s.
This evidence suggests that the high
growth rates of U.S. output in the 1990s

have not been due to an increase in
the underlying trend growth rate but
rather to temporary unobservable factors that have permanently raised the
level of trend output.
Conclusion
The popular press has hailed the
dawn of a new paradigm in which the
U.S. economy can expand at rates
much greater than the past without
igniting higher levels of price inflation. This concept is based on the
belief that the U.S. experienced a
structural change in the 1990s that
raised its trend growth rate. Evidence
presented here, which is based on one
set of statistical tests, suggests that the
underlying trend growth rate of U.S.
output has not increased in the 1990s.
In fact our estimates suggest that
the trend rate of growth has merely
returned to the levels of the early
1980s. Overall, our statistical model
suggests that the robust performance
of the U.S. economy has been due
to temporary factors that have permanently raised the level of U.S. production, but have not changed the longrun growth rate of the U.S. economy.
—Margaret K. Burke
Associate economist

macroeconomic time series: Some evidence and implications,” Journal of Monetary Economics, Vol. 10, pp. 139–162.
6

S. Beveridge and C. R. Nelson, 1981, “A
new approach to decomposing economic
time series into permanent and transitory components with particular attention
to measurement of the ‘business cycle’,”
Journal of Monetary Economics, Vol. 7,
pp. 151–174.

7

R. Hodrick and E. Prescott, 1997, “Postwar U.S. business cycles: An empirical
investigation,” Journal of Money, Credit,
and Banking, Vol. 29, pp. 1–16.

8

M. Baxter and R. G. King, 1998, “Measuring business cycles: Approximate bandpass filters for economic time series,”
International Economic Review, forthcoming.

9

M. W. Watson, 1986, “Univariate
detrending methods with stochastic
trends,” Journal of Monetary Economics,
Vol. 18, pp. 49–75.

10

M. K. Burke and M. A. Kouparitsas, 1998,
“Technical appendix: A new paradigm
for the U.S. economy?,” Federal Reserve
Bank of Chicago, manuscript, forthcoming.

11

Baxter and King’s band-pass filter is
approximated by a two-sided moving
average, with a lag length of 12, so we
lose the first and last 12 observations.

Michael A. Kouparitsas
Economist
1

M. J. Mandel, 1997, “The new business
cycle,” Business Week, March 31, pp. 58–
68, and S. B. Shepard, 1997, “The new
economy: What it really means,”
Business Week, November 17, pp. 38–40.
2

R. J. Barro and X. Sala-i-Martin, 1992,
“Convergence,” Journal of Political
Economy, Vol. 100, pp. 223–251.

3

S. T. Rebelo, 1991, “Long-run policy
analysis and long-run growth,” Journal
of Political Economy, Vol. 99, pp. 500–521.

4

R. G. King, C. I. Plosser, and S. T. Rebelo, 1988, “Production, growth and business cycles: The basic neoclassical
model,” Journal of Monetary Economics,
Vol. 21, pp. 195–232.

5

C. R. Nelson and C. I. Plosser, 1981,
“Trends and random walks in

Michael H. Moskow, President; William C. Hunter,
Senior Vice President and Director of Research; Douglas
Evanoff, Vice President, financial studies; Charles
Evans, Vice President, macroeconomic policy research;
Daniel Sullivan, Vice President, microeconomic policy
research; William Testa, Vice President, regional
programs; Vance Lancaster, Administrative Officer;
Helen O’D. Koshy, Editor.
Chicago Fed Letter is published monthly by the
Research Department of the Federal Reserve
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Tracking Midwest manufacturing activity
Manufacturing output indexes, 1992=100
137.0

Manufacturing output indexes
(1992=100)
July

Month ago

CFMMI

121.2

124.5

Year ago
123.0

IP

129.3

130.2

126.9

IP

127.0

Motor vehicle production
(millions, seasonally adj. annual rate)
Cars
Light trucks

July

Month ago

Year ago

3.9
4.0

4.8
5.2

5.8
4.9

CFMMI

117.0

Purchasing managers’ surveys:
net % reporting production growth
MW
U.S.

Aug.

Month ago

Year ago

59.2
50.3

52.0
49.2

59.9
62.4
107.0

1995

1996

The Chicago Fed Midwest Manufacturing Index (CFMMI) decreased 2.6% in
July following a revised decrease of 1.7% in June. The Federal Reserve Board’s
Industrial Production Index (IP) for manufacturing declined 0.7% in July after declining 1.2% in June.
The Midwest purchasing managers’ composite index increased to 59.2% in
August from 52.0% in July. Purchasing managers’ indexes increased in both
Detroit and Milwaukee, but the index decreased in Chicago. Total light motor
vehicle production decreased to 7.9 million units in July from 10.0 million
units in June. Light truck production decreased to 4.0 million units in July
from 5.2 million units in June and car production decreased to 3.9 million
units from 4.8 million units during this period.

1997

1998

Sources: The Chicago Fed Midwest Manufacturing Index (CFMMI) is a composite index of 16
industries, based on monthly hours worked and
kilowatt hours. IP represents the Federal Reserve Board’s Industrial Production Index for
the U.S. manufacturing sector. Autos and light
trucks are measured in annualized units, using
seasonal adjustments developed by the Board.
The purchasing managers’ survey data for the
Midwest are weighted averages of the seasonally adjusted production components from the
Chicago, Detroit, and Milwaukee Purchasing
Managers’ Association surveys, with assistance
from Bishop Associates, Comerica, and the
University of Wisconsin–Milwaukee.

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