speeches · September 8, 2013
Regional President Speech
John C. Williams · President
Presentation to the National Association for Business Economics
San Francisco, California
By John C. Williams, President and CEO, Federal Reserve Bank of San Francisco
For delivery on September 9, 2013
Bubbles Tomorrow and Bubbles Yesterday, but Never Bubbles Today?1,2
Thank you. It’s a pleasure to be here at NABE’s 55th annual meeting. Your organization
has done as much as any to support the profession and promote discussion of the most important
economic questions of our time, so it’s a privilege to join you.
In my talk this morning, I will focus on an issue that has fascinated and perplexed
economists for centuries—asset price bubbles. Obviously, the events of the past two decades
demonstrate that this topic is not merely of academic interest. Asset price booms and busts
distort the course of the economy and can leave enormous economic wreckage in their trail. In
considering this topic, I’ll start by reviewing the basics of asset price theory. I’ll then highlight
some striking inconsistencies between theory and evidence in standard models of asset prices.
I’ll then explore some recently developed theories that may help explain why bubbles sometimes
form and why they crash. And I’ll close with some speculation about the implications for
monetary and macroprudential policy. I should add that my remarks represent my own views
and not necessarily those of others in the Federal Reserve System.
We economists like to explain things using highly stylized models. We build make-
believe worlds, populate them with creatures that act according to strictly prescribed rules, and
1 I want to thank Kevin Lansing and Sam Zuckerman for their assistance in preparing these remarks.
2 The title is a reference to Through the Looking-Glass and What Alice Found There, by Lewis Carroll (1871). The
White Queen offers Alice “jam every other day” as an inducement to work for her:
“I’m sure I’ll take you with pleasure!” the Queen said. “Two pence a week, and jam every other day.”
Alice couldn’t help laughing, as she said, “I don’t want you to hire me—and I don’t care for jam.”
“It’s very good jam,” said the Queen.
“Well, I don’t want any to-day, at any rate.”
“You couldn’t have it if you did want it,” the Queen said. “The rule is, jam to-morrow and jam yesterday—but
never jam to-day.”
1
analyze what happens. Or, as my wife said after I described one of my research papers to her:
“You really never did stop playing Dungeons and Dragons, did you?” The thing is, most of the
time, this approach works remarkably well. Often, the simplest model—with patently unrealistic
assumptions—yields the keenest insights into how a market or an economy works. Without
doubt, Occam’s razor has proven to be a most valuable item in the economics toolkit.
Unfortunately, asset prices have proven less amenable to this kind of treatment. A
cursory reading of the academic literature on asset prices reveals a litany of puzzles,
conundrums, paradoxes, and anomalies. Much of the research on asset prices continues to rely
on highly stylized models with identical agents, rational expectations, and optimizing behavior.
According to the prevailing view, asset price surges that many would perceive to be bubbles are
not really so. Instead, they are seen to reflect the influences of fundamental forces, such as a
decline in risk appetite. This reminds me of the White Queen in Through the Looking-Glass,
who says jam will be given every other day, but never today. Adherents of this view may admit
that bubbles have occurred in the past—like the dot-com boom and bust. And they may even be
willing to accept that bubbles are something to worry about in the future—say, in financial
supervision. But, in practice, they are never willing to find a bubble in the present. There’s
always a reason why what looks like a bubble, walks like a bubble, and quacks like a bubble is
not actually a bubble. But, as I’ll discuss in a moment, this is changing. Recent research not
only recognizes that asset price bubbles really do form, but also holds great promise in unlocking
their secrets and identifying them.
Let’s now consider standard asset price theory, according to which the price of an asset
equals the discounted expected return of holding the asset for one period. For example, take a
share in a corporation. The return consists of two parts: the dividend payment the owner
2
receives and the capital gain or loss from selling the share. The same formula applies to owning
a house or a bond, or any asset for that matter. For the house, the dividend payment is the
service flow the owner derives from living in it or renting it out. For the bond, it is the coupon
payment. According to this theory, three variables can affect asset prices: the discount factor, the
dividend payment, and the expected future price appreciation.
It helps to simplify things a bit further. Under certain assumptions, including the absence
of bubble-like behavior, Myron Gordon developed over 50 years ago an illuminating way of
presenting this asset price formula. He noted that the ratio of the asset price to the dividend
payment is inversely related to the difference between the expected future rate of return and the
growth rate of inflation-adjusted dividends.3 That is, all else equal, the price-to-dividend ratio
should be high when expected future dividend growth is high or when the expected future return
to the asset is low. This is a classic case of an elegant and parsimonious theory. So, how does it
stand up to the data?
The first hurdle the model faces is the long history of boom and bust cycles in a variety of
different asset prices. These were thoroughly documented by Robert Shiller in his book
Irrational Exuberance.4 I’m an economist, so I need to show some numbers here. Figure 1
shows two well-known recent U.S. asset price booms and busts. The solid blue line shows the
price-to-dividend ratio of the S&P 500 stock index from 1990 to the present. The dashed red line
shows the time series of the house price-to-rent ratio from the CoreLogic home price index, in
which the rent data are the Bureau of Economic Analysis data on owners’ equivalent rent. In the
stock market boom of the late 1990s, the price-to-dividend ratio rose over 100 percent in the five
years up to the end of the boom in 2000. The recent housing boom was relatively tame by this
3 Gordon (1959).
4 Shiller (2005). Another must-read is Kindleberger’s Manias, Panics, and Crashes (1978).
3
standard. The house price-to-rent ratio climbed around 50 percent during the five years before
the market peak in 2006. To put these numbers in perspective, according to flow of funds data,
in the five years before they peaked, U.S. stock market wealth soared $12 trillion and housing
wealth increased some $10 trillion.
What does the Gordon model have to say about these and other large surges in asset
prices? Two explanations are possible based on changes in economic fundamentals. One is an
upward shift in the expected growth rate of future dividends. The second is a reduction in
investors’ expected returns on the asset. Importantly, in standard asset pricing theory,
expectations of future dividend growth and future returns on assets are assumed to be rational.
That is, expectations are assumed to be consistent with the structure of the model.
I’ll start with the first explanation, that a rise in the price-to-dividend ratio is caused by
higher expected dividend growth. The evidence on this is clear and negative. With respect to
U.S. stocks, over history, the price-to-dividend ratio is uncorrelated with future real dividend
growth.5 A similar pattern is seen with regard to the U.S. housing market. The price-to-rent
ratio is uncorrelated with future real rent growth.6 The international evidence is somewhat more
mixed. But a recent cross-country study found that, in most countries, the correlation between
the house price-to-rent ratio and future real rent growth is either statistically insignificant or has
the opposite sign of that predicted by the theory.7 Indeed, in the most recent U.S. housing boom,
the high house price-to-rent ratio observed during the boom did not foreshadow subsequent high
real rent growth. In fact, the growth rate of real rents actually declined in the period following
the peak price-to-rent ratio. It’s simply not the case that asset price movements can be explained
by shifts in rational expectations of future dividend growth.
5 Cochrane (2008).
6 Campbell et al. (2009) and Gelain and Lansing (2013).
7 Engsted and Pedersen (2012).
4
So that leaves the possibility that a lower expected return might be driving the increase in
asset prices during a boom. The lower expected return could reflect a combination of lower
alternative investment returns, say as measured by the general level of real interest rates, and/or a
lower risk premium on the asset in question. As in the case of dividend growth, the evidence on
expected future real interest rates driving asset prices is negative. Equity dividend-to-price ratios
are generally not correlated with future changes in real interest rates.8
Thus, expectations of future dividends or real interest rates fail to explain asset price
movements. Given that, standard approaches ascribe much of the variation in asset prices to
movements in the discount factor used to compute the present value of future dividends. This is
the logic of Sherlock Holmes, who said that, “when you have eliminated the impossible,
whatever remains, however improbable, must be the truth.”9 Time variation in the discount
factor is the only remaining rational explanation. However, on their own, you can’t really judge
whether movements in the discount factor are reasonable. After all, they are simply defined as
the residual component of an identity implied by the theory. In this regard, the discount factor is
akin to total factor productivity, which Moses Abramovitz famously described as “a measure of
our ignorance.”10
Moreover, the explanation that the discount factor is the main driver of movements in the
price-to-dividend ratio has potentially falsifiable implications. In particular, it says that when the
price-to-dividend ratio is high, rational investors should expect a relatively low rate of return on
the asset. When valuations are low, rational expected returns should be high.11 For example, if
rational investors discount future dividends by less, perhaps owing to a reduction in risk
8 Campbell and Shiller (1988).
9 The Sign of the Four by Arthur Conan Doyle (1890).
10 Abramovitz (1956).
11 Greenwood and Shleifer (2013).
5
aversion, then the price-to-dividend ratio rises and we see a boom in the asset price. And the
expected future rate of return on the now higher-priced asset will be correspondingly lower.
So, are the data consistent with this prediction of the theory? One test is to compare real-
world measures of investors’ expected returns with the expected returns implied by the theory.
Fortunately, there are a number of surveys of investor expectations of future returns on stocks
and houses that can be brought to bear on this question.
Let me jump to the bottom line. The evidence from surveys of investors’ expected
returns is directly at odds with the implications of standard asset price theory. For one, stock
market investors tend to expect high future returns when the price-to-dividend ratio is high,
contrary to the theoretical prediction of a negative relationship between rational expected returns
and the level of asset prices relative to dividends.12 A picture tells the story. Figure 2 shows
Gallup survey results on the relationship between the S&P 500 price-to-dividend ratio and
investor optimism regarding stock market returns over the next year. Gallup asks whether
people are optimistic, pessimistic, or neutral about future market returns. The figure reports the
difference between the number saying they are optimistic or very optimistic and those saying
they are pessimistic or very pessimistic. As the figure shows, periods of high stock valuations,
such as the late 1990s and mid-2000s, are when investors were more optimistic regarding future
stock gains. And during periods of relatively low valuations, such as the early 2000s and the
period of the global financial crisis, investors had relatively low expectations of stock market
returns. The positive relationship between current stock prices and expected future returns is
consistent across a variety of surveys and alternative model specifications.
This same relationship is evident in data on house prices. Figure 3 plots the level of
house prices and expected future house price appreciation in the United States over the past
12 Greenwood and Shleifer (2013). Thanks to the authors for supplying data used in Figures 2 and 4.
6
decade. Each data point represents one of four major cities in a given year.13 The pattern is
clear. Optimism about future house price appreciation tends to increase when house prices are
high. Just as with stocks, the survey evidence directly contradicts the fundamental story that
high house prices can be explained by a decline in the rational expected return from
homeownership.
Let me sum up my points so far. According to standard asset price theory, an increase in
asset prices must reflect either an increase in expected future dividend growth or a reduction in
the expected return on the assets. We see large run-ups in equity and home prices. But they are
not associated with higher future dividend growth rates or lower expected returns based on
surveys. So far, this evidence is mainly destructive. But, in fact, a first step to understanding
asset price bubbles can be found in the survey data I just discussed. The key is to relax the
assumption of rational expectations and allow people’s decisions to be driven by their
perceptions of what the future may hold.
A striking regularity seen in the survey data is that expectations of future gains are highly
positively correlated with past observed returns. That is, despite the admonition that past
performance is no guarantee of future results, people appear to assume exactly that in predicting
future stock returns. Figure 4 shows the relationship between the Gallup survey of investor
optimism about future stock market gains and the trailing 12-month change in the S&P 500 stock
price index. The correlation is strongly positive. Indeed, the worst reading for the investor
optimism index for the period shown in the figure occurred in early 2009, just as the stock
market plunged to its recession low. And the highest reading of investor optimism occurred in
early 2000, just before the tech stock crash. The evidence is compelling. People tend to
extrapolate future stock price movements from recent stock price performance. This finding is
13 Case, Shiller, and Thompson (2012).
7
confirmed by econometric analysis that uses different measures of investor expectations and
controls for various other factors.14
The same dynamic of extrapolative expectations also plays out in housing markets in the
United States and abroad. Figure 5 shows the relationship between expected house price
appreciation over the next year from surveys and the percentage change in house prices observed
over the prior year for four major U.S. cities over the past decade. As in the case of stock prices,
the correlation is strongly positive. Figure 6 shows similar patterns for Norway and Sweden, two
other countries that have experienced massive house price booms.15 Just as in the United States,
when house prices go up, people expect them to continue to rise. And when they fall, people
turn much more pessimistic about future house price appreciation.
Many researchers are probing why people have the procyclical pattern of optimism seen
in these surveys. One key element in the theories coming out of this research is that people do
not possess the full set of information assumed in the standard asset price model with rational
expectations. Instead, they must make do with the limited information at hand when judging
likely future discounted dividend payments and the future price of the asset. Indeed, a growing
body of evidence in behavioral economics and finance shows that people’s expectations of future
asset returns depend on their past experiences.16 This process of forecasting with limited
information has been shown to cause forecast errors that can drive a wedge between asset prices
and the values implied by economic fundamentals.17
The recognition that people behave this way can move us a long way closer to
understanding how asset price bubbles can emerge and how they can crash. To see this, let me
14 Greenwood and Shleifer (2013).
15 Jurgilas and Lansing (2013).
16 Vissing-Jorgensen (2003) and Malmendier and Nagel (2011).
17 Cutler, Poterba, and Summers (1991) and Barsky and DeLong (1993).
8
return to the standard asset price formula. Recall that the price of an asset equals the value of its
dividend plus the discounted value of the price at which you expect to be able to sell the asset. If
one then assumes that investors’ expected price appreciation of the asset depends positively on
its recent past price change, this introduces a positive feedback loop into asset price dynamics
that is absent from the standard model assuming rational expectations. Indeed, a simple model
of extrapolative expectations of future asset price movements does a very good job of explaining
the big swings in the U.S. stock price-to-dividend ratio over time.18
This principle has proven a good model of investor expectations. But a challenge to
models based on extrapolative expectations is that they may create too much positive feedback in
asset prices, producing excess volatility at odds with the data. Despite the failures of standard
asset price theory, the price-to-dividend ratio is a good predictor of future excess returns on the
stock market relative to the risk-free rate.19 That is, a high price-to-dividend ratio today predicts
relatively low average future stock returns. Therefore, for a model to succeed, it needs to allow
for procyclical investor optimism, while incorporating a self-stabilizing mechanism that
eventually stops and reverses this process, bringing prices back toward fundamental values. This
is a delicate balance. One promising approach is to posit two types of traders, one with
extrapolative expectations and the other that trades based on fundamentals.20 In a nutshell, the
traders with extrapolative expectations drive the procyclical optimism, while the fundamental
traders exert a stabilizing influence that keeps things from going completely off the rails.21
Researchers have yet to coalesce around one preferred model. However, a common
theme in this literature is that the presence of a small amount of sand in the ability of people to
18 Adam, Beutel, and Marcet (2013).
19 Cochrane (2008).
20 Cutler, Poterba, and Summers (1990) and Greenwood and Shleifer (2013).
21 For an alternative approach, see Adam et al. (2013).
9
process information can lead to large and sustained swings in asset prices, with significant
repercussions for the economy. An important implication of these models is that
nonfundamental asset price movements do not represent exogenous “shocks” to the economy.
Rather, they are part of the endogenous behavior of the economic system. In particular, these
asset price movements tend to amplify and propagate other shocks that occur within the system.
This recognition of the source of asset price movements means that work on monetary
and macroprudential policies needs to refocus on how these policies may damp or amplify asset
price cycles, rather than how they should respond to asset prices per se. For monetary policy,
one implication of theories with endogenous asset price bubbles is that the time horizon over
which policy affects the economy may be longer than typically thought. In particular, the policy
response to cyclical movements in economic activity and inflation may have effects on investor
beliefs and the behavior of asset prices that reach well into the future.
The lesson from history is clear: asset price bubbles and crashes are here to stay. They
appear to be a consequence of human nature.22 And the events of the past decade demonstrate
the enormous human costs of asset price bubbles and crashes.
To understand the past and avoid a recurrence of the devastating events we lived through
so recently, we need to acknowledge that investors and financial markets do not behave the way
rational asset price theory implies. We need to incorporate these channels into the models we
use for forecasting, risk analysis, and policy evaluation. This opens up a world where actions,
including regulatory and monetary policy measures, may have unintended consequences—such
as excessive optimism, risk taking, and the formation of bubbles—that are assumed away in
standard rational models.
22 Kindleberger (1978).
10
Of course, this is a difficult task, and successful models are likely to be far more
complicated than the simple and elegant rational models we have relied on in the past. But, it’s
essential if we want to design policies that foster robust economic performance in the future.
Thank you.
11
Figure 1
Asset Price Booms and Crashes
Ratio
3
S&P 500
price-to-dividend ratio
2.5
2
1.5
CoreLogic 1
house price-to-rentratio
Normalized to 1
0.5
in January 1995
0
90 92 94 96 98 00 02 04 06 08 10 12
Sources: CoreLogic,BEA, and S&P 500 data from Shiller (2005, updated).
Figure 2
Stock Prices and Investor Optimism
% Optimistic -% Pessimistic
80
60
40
20
0
Fitted line
-20
-40
-60
0.5 1 1.5 2 2.5 3
S&P500 Price-to-Dividend Ratio
Sources: Greenwood and Shleifer (2013), Wells Fargo/Gallup, and S&P 500 data from Shiller (2005, updated). Data from 1996 to 2013.
12
Figure 3
House Prices and Expected Price Appreciation
Expected 1-year house price change (percent)
14
12
10
8
Fitted line
6
4
2
0
-2
-4
100 120 140 160 180 200 220 240 260 280
HousePrice Index
Sources: S&P/Case-Shiller,FHFA, and Case, Shiller, and Thompson (2012). Cities included are San Francisco/Alameda
County, Boston, Los Angeles/Orange County, and Milwaukee. Datafrom 2003 to 2012.
Figure 4
Extrapolative Expectations in the Stock Market
% Optimistic -% Pessimistic
80
Fitted line 60
40
20
0
-20
-40
-60
-60 -40 -20 0 20 40 60
Trailing 12-month change in S&P500 (percent)
Sources: Greenwoodand Shleifer (2013), Wells Fargo/Gallup, and S&P 500 data from Shiller (2005, updated).Data from 1996 to 2013.
13
Figure 5
Extrapolative Expectations in the Housing Market
Expected 1-year house price change (percent)
14
12
Fitted line
10
8
6
4
2
0
-2
-4
-30 -20 -10 0 10 20 30 40
Trailing 12-monthchange in house price indexes (percent)
Sources: S&P/Case-Shiller,FHFA, and Case, Shiller,and Thompson (2012).Citiesincluded are San Francisco/Alameda
County, Boston, Los Angeles/Orange County, and Milwaukee. Data from 2003 to 2012.
Figure 6
Extrapolative Expectations in Scandinavia
Norway Sweden
Balance of positive and negative house price expectations (percent) Balance of positive and negative house price expectations (percent)
80 80
60
Fitted line 60
40
40
20
20 0
Fitted line
-20
0
-40
-20
-60
-40 -80
-10 -5 0 5 10 15 20 -5 0 5 10 15
Trailing 12-monthchange in house price (percent) Trailing 4-quarter change in house price (percent)
Source: Jurgilasand Lansing (2013), data from 2007to 2012. Source: Jurgilas and Lansing (2013), data from 2003 to 2012.
14
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Cite this document
APA
John C. Williams (2013, September 8). Regional President Speech. Speeches, Federal Reserve. https://whenthefedspeaks.com/doc/regional_speeche_20130909_john_c_williams
BibTeX
@misc{wtfs_regional_speeche_20130909_john_c_williams,
author = {John C. Williams},
title = {Regional President Speech},
year = {2013},
month = {Sep},
howpublished = {Speeches, Federal Reserve},
url = {https://whenthefedspeaks.com/doc/regional_speeche_20130909_john_c_williams},
note = {Retrieved via When the Fed Speaks corpus}
}