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ESSAYS ON ISSUES
	

	 THE FEDERAL RESERVE BANK	
OF CHICAGO

2015
	 NUMBER 344

Chicag­ Fed Letter
o
Recent trends in capital accumulation and
implications for investment
by François Gourio, senior economist, and Thomas Klier, senior economist and research advisor

Business investment has been fairly low over the past several years. As a result, the
growth in the stock of capital has not kept up with the growth in gross domestic product
(GDP) or employment. This Chicago Fed Letter studies these recent trends and discusses
their implications for future investment.

One manifestation of economic growth
has been the increase in the capital–labor
ratio—the quantity of equipment and
other productive assets available for
each worker to produce
1. Capital–output ratio (K/Y)
goods and services. Over
the past four decades,
log index
we have also observed
a significant increase
0.4
in the capital–output
ratio—the quantity of
productive assets rela0.3
tive to GDP. The increase
in these capital ratios
0.2
reflects the accumulation of assets thanks to
0.1
higher productivity—
in particular the avail0.0
ability of cheaper, more
efficient capital goods,
such as computers. In
–0.1
turn, these higher capi1950
’60
’70
’80
’90
2000
’10
tal ratios allow higher
Notes: The shaded areas represent recessions as classified by the National Bureau
of Economic Research.
productivity and a highSource: U.S. Bureau of Labor Statistics.
er standard of living
per worker.

However, relatively weak business investment over the past few years has led
to a slowdown in the growth of the capital stock. Views differ on how to interpret this fact. Some argue that the weak
investment is the consequence of excess
investment experienced before the recent
recession. Others argue that it merely

reflects weak output growth, owing
perhaps to contemporaneously deficient demand or lower productivity
growth. And some believe that the underaccumulation of capital means the U.S.
economy is poised for a large increase
in investment if the current expansion
continues. This leads us to consider two
questions. First, where does the U.S.
economy currently stand in terms of capital accumulation? And second, what does
this tell us about future investment?
Is capital currently on track?

Figures 1 and 2 depict the capital–output
and capital–labor ratios for the period
from 1950 to 2014. In both figures, the
shaded areas represent recessions as
classified by the National Bureau of
Economic Research (NBER). We use
annual real data produced by the U.S.
Bureau of Labor Statistics (BLS) multifactor productivity program.1 Three
facts are evident from these figures.
First, both ratios have been on a positive
trend. The capital–output ratio was stable until around 1970 before starting
a secular rise, which brought it up by
around 30% by the beginning of the most
recent recession. The capital–labor
ratio has grown steadily and significantly
since World War II, by 1.5 log points,
which translates into growth by a factor
of around 4.5. Second, both of these

2. Capital–labor ratio (K/L)

3. Deviations (in log points) from linear trend as of 2014

log index

Sample used for trend:		

1.8

Start date	

1995	 1995	1985	 1985	1979	
1979

End date	

2007	 2014	2007	 2014	2007	
2014

1.6

Deviations from trend of:		
1.4

Capital–output
ratio	

1.0

–0.058	 –0.046	 –0.042	 –0.045	 –0.063	 –0.055

Capital–labor
ratio	

1.2

–0.200	 –0.096	 –0.100	 –0.084	 –0.078	 –0.077

Source: Authors’ calculations based on data from the U.S. Bureau of Labor Statistics.

0.8
0.6
0.4

4. Source of the deviation from trend

0.2

All entries in percent	

0
1950

K/Y	K/L

Deviation from trend in 2007	
’60

’70

’80

’90

2000

’10

Notes: The shaded areas represent recessions as classified by the National Bureau
of Economic Research.
Source: U.S. Bureau of Labor Statistics.

–1.3	

–0.2

+ Numerator (K) growth 2007–14	

10.8	

10.8

– Denominator (Y or L) growth 2007–14	

9.2	

2.3

– Required trend growth 2007–14	

4.5	

19.4

–4.2	

–9.5

= Deviation from trend in 2014	

Source: Authors’ calculations based on data from the U.S. Bureau of Labor Statistics.

ratios exhibit a pronounced cyclical
pattern: They increase during recessions
and subsequently fall during recoveries.
The ratios then flatten out before starting to grow again. This pattern simply
reflects the fact that the stock of capital
(the numerator in both ratios) changes
more slowly than either production or
employment. Third, the recent Great
Recession is no outlier—it has followed
the historical pattern but has been more
pronounced owing to the historically
large fluctuation experienced at the time.
In terms of current conditions, both the
capital–output and the capital–labor
ratios are shown to currently lie below
their respective trend lines. To measure
the extent of this gap, we estimate a
linear trend for both the log capital–
output and log capital–labor ratio. Figure 3 presents the estimated deviation
from trend for both measures as of 2014.
Because trend lines can be sensitive to
the specific window of time used to estimate the trend, we construct a variety
of estimates, corresponding to different
starting and ending dates (figures 1
and 2 show the trend from 1985 to 2014).
Regardless of which dates we use, figure 3 shows that the capital–output
ratio is currently 4% to 6% below its
trend, while the capital–labor ratio is
7% to 10% below its trend (excluding

the most extreme estimate of 20%).
Overall, this exercise shows that relative
to output or labor, capital formation in
the United States is currently growing
well below trend.
Where does this imbalance come from?

Before turning to our second question
it is perhaps worthwhile to ask how the
U.S. economy has fallen so far below
trend. Figure 4 provides a simple decomposition of the deviation from trend
for both ratios. It starts in 2007, the
most recent year in which the capital–
output and capital–labor ratios were not
far from trend. As a matter of accounting,
the current deviation from trend (at the
end of 2014) is the sum of the starting
deviation in 2007 and capital growth
accumulated since 2007, less the growth
in output (or labor) since 2007 and the
required growth to keep up with the
trend line.2 Overall, we see that capital
growth since 2007 has been too weak,
even relative to the disappointing growth
in output or labor, to sustain the trend.3
Of course, such an accounting exercise
does not imply causality. Capital growth
may well have been slow, in part, because output growth was slow. That is,
there need not have been a specific
factor that impeded investment.4

Looking ahead

We can now turn to our second question:
What does the current situation tell us
about future business investment? If
capital–output (or capital–labor) is to
return to its trend line, the current deviation from trend must be corrected.
This can happen either through an increase in the numerator—an increase
in capital, i.e., a significant increase in
investment—or through a decrease in
the denominator—i.e., a contraction in
output or labor. Figure 5 presents some
simple linear regressions to shed light
on this question. In this exercise the
dependent variable is the growth rate
of capital; the right-hand side variables
are the lagged growth rate of capital, a
constant and a linear trend, the lagged
capital–output ratio (or capital–labor
ratio) and lagged output growth (or labor
growth).5 We first present (in the first
two columns) the results of this model
for the aggregate capital stock. However,
because the three major subcomponents
of investment spending (spending on
equipment, structures, and intellectual
property) have exhibited very different
trends over the past 30 years, we also
estimate a separate model for each of
these subcomponents. We show the results of this exercise in the remaining
columns of figure 5. For simplicity, we

	 5. Dynamics of adjustment of capital
	

Aggregate capital	

Lagged capital–output ratio	

–0.07			

–0.15**			

–0.01	

–0.09**	

Standard error	

(0.06)			

(0.05)			

(0.01)		

(0.04)	

Lagged capital–labor ratio		

Equipment	

–0.06*			

Structures	

–0.08*		

Intellectual property

–0.02**		

–0.08**

Standard error		
(0.04)		
(0.04)		
(0.01)		
(0.03)
R2	

0.92	0.90	

0.93	 0.90	

0.95	 0.98	

0.94	

0.94

Start date	

1985	

1985	

1987	

1987	

1987	

1987	

1987	

1987

End date	

2014	

2014	

2013	

2013	

2013	

2013	

2013	

2013

Notes: Asterisks indicate statistical significance at 1% (***), 5% (**), or 10% (***) level, measured using ordinary least squares standard errors. See text for variables and specification.
Source: Authors’ calculations based on data from the U.S. Bureau of Labor Statistics.

only report the coefficient on the lagged
capital–output or capital–labor ratio.
The key message from the figure is that
future capital growth tends to be high,
when the current capital–output (or
capital–labor) ratio is low. Most of these
results are statistically significant at conventional levels, especially when we estimate the model separately for each
component of capital. (On the other
hand, in results not shown here, we find
no statistically significant effect of lagged
capital–output or capital–labor ratio
on future output or labor growth; even
the sign of the slope coefficient is not
uniform across regressions.) Overall,
we expect that the deviation from trend
of the capital ratios will be corrected
mostly through adjustment in capital.
Most economists, however, focus on
investment rather than capital growth.
This leads us to conduct a final simple
exercise to quantify how much the
current value of the capital–output or
capital–labor ratio affects the outlook
for investment. We compare two simple
forecasts for the investment–capital
ratio: The first comes from a model
that uses only the lagged investment–
capital ratio, lagged output growth, and
a deterministic trend. The second comes
from a model that has the same variables,
plus the capital–output (or capital–labor)
ratio. This second model turns out to
predict growth in investment spending
of an additional 1.3% to 1.6%. Breaking it down into its major components
suggests that most of the additional expected growth comes from equipment

and intellectual property, while structures
lead to lower expected growth because
the current capital stock remains above
the estimated trend. This last finding is
consistent with the idea of an “overhang”
(i.e., a residual of past overinvestment)
in commercial real estate.
Conclusion

Overall we find that capital currently is
below its longer-term trend in relation
to both output and labor. If historical
patterns hold, this suggests some additional growth of investment going forward, of perhaps a little over 1 percentage
point per year while the current imbalance lasts. However, this relationship is
statistically fragile, owing in part to the
relative sparsity of data. There are two
additional concerns. First, the trend of
capital accumulation may be unstable.
In particular, a persistent decline in
productivity growth could lead to lower
desired capital accumulation and could
make the current level of capital sufficient. Second, recent investment may
have been underestimated.6 In that case,
the current capital ratios would be underestimated and our analysis would
overestimate the extent of their deviation from trend.
	 The capital index produced by the BLS
differs from the one produced by the U.S.
Bureau of Economic Analysis (BEA) in the
fixed-assets tables. The BLS index is a better
measure of aggregate capital as an input
in production because it aggregates capital
stocks using estimated rental prices. The
BEA aggregates using resale prices instead,
resulting in a better measure of wealth.

1

There are also some differences in the depreciation rates used. The two measures
have been diverging since 1980, likely
reflecting that high-tech equipment has
high depreciation, and hence high rental
rates, but quickly declining resale values.
As a measure of output, we use nonfarm
business sector output; for labor, we use a
quality-adjusted index produced by the BLS.
	 For this calculation, we use the trend estimated from 1985 to 2014.

2

	 By comparison, over the previous seven
years, 2000 through 2007, capital growth
was 25.4%, output growth 21.5%, and labor
growth 3.8%.

3

Charles L. Evans, President; Daniel G. Sullivan,
Executive Vice President and Director of Research;
David Marshall, Senior Vice President and Associate
Director of Research; Spencer Krane, Senior Vice
President and Senior Research Advisor; Daniel Aaronson,
Vice President, microeconomic policy research; Jonas D. M.
Fisher, Vice President, macroeconomic policy research;
Anna L. Paulson, Vice President, finance team;
William A. Testa, Vice President, regional programs,
and Economics Editor; Helen Koshy and Han Y. Choi,
Editors; Julia Baker, Production Editor; Sheila A.
Mangler, Editorial Assistant.
Chicago Fed Letter is published by the Economic
Research Department of the Federal Reserve Bank
of Chicago. The views expressed are the authors’
and do not necessarily reflect the views of the
Federal Reserve Bank of Chicago or the Federal
Reserve System.
© 2015 Federal Reserve Bank of Chicago
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ISSN 0895-0164

	 Indeed, when we simulate a simple model
for capital growth (a regression of capital
growth on lagged capital growth, lagged
output growth, the lagged capital–output
ratio, a constant, and a linear trend), we
find that the low output growth “explains”
a significant fraction of capital growth. Consequently, when we simulate the capital–
output ratio given data on output growth
with this simple model, we find that the

capital–output ratio is only about 1% lower than the model implies. Similar results
hold for the capital–labor ratio.

4

	 Technically, these regressions are well
specified if capital and output (or labor)
are, in logs, cointegrated around a linear
trend. A Dickey–Fuller test can reject the
null that the log capital–output has a unit
root since 1980, but cannot reject it for
the log capital–labor.

5

	 This possibility was discussed recently by
economists at the Board of Governors of
the Federal Reserve System. See http://
www.federalreserve.gov/econresdata/
notes/feds-notes/2015/recent-slowdownin-high-tech-equipment-price-declinessome-implications-for-business-investmentlabor-productivity-20150326.html.

6