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For release on delivery
10:10 a.m. EDT (4:10 p.m. local time)
March 16, 2006

Remarks by

Donald L. Kohn

Member

Board of Governors of the Federal Reserve System

at
Monetary Policy: A Journey from Theory to Practice
An ECB Colloquium held in honor of Otmar Issing

Frankfurt, Germany

March 16,2006

I am honored to participate in this tribute to Otmar Issing. I have known and
admired Otmar for some time. It has been a source of great pride that he has considered
me a worthy intellectual sparing partner over the years. From the hiking trails of Jackson
Hole to the restaurants of Frankfurt and at many conferences in between, we have
challenged each other to state our assumptions, examine the evidence, and adjust our
conclusions accordingly. I have derived enormous benefit from that give-and-take--a
sentiment, I am sure, that many others in this room share.
I can think: of no better way to celebrate the signal contributions of this leading
force in the world of monetary policymaking than to address an issue of great importance
to central banks, and one that has drawn considerable public attention and comment of
late--namely, the proper role of asset prices in the determination of monetary policy.
Otmar and I have debated this issue on many occasions, and these discussions--together
with recent research carried out at the European Central Bank, the Bank for International
Settlements, and elsewhere--have been both challenging and stimulating. The
preparation of this talk has afforded me a welcome opportunity to reexamine my thinking
on this subject. So, today, I will review the arguments and the evidence as I see them and
draw out the conclusions to which I am currently led.
At the outset, let me stress that I will be expressing my own opinions, which are
not necessarily shared by my colleagues on the Federal Open Market Committee. l

Two Strategies for Dealing with Market Bubbles
Most fluctuations in stock prices, real estate values, and other asset prices pose no
particular challenge to central banks, as they are just some of the usual factors
influencing the outlook for real activity and inflation. But many argue that pronounced

-2booms and busts in asset markets are another matter, especially if actual valuations
appear to be misaligned with fundamentals. What should a central bank do when it
suspects it faces a major speculative event--one that might be large enough to threaten
economic stability when it unwinds? To help frame the discussion, I will focus on two
different strategies that have been proposed for dealing with market bubbles.
The first approach--which I will label the conventional strategy--calls for central
banks to focus exclusively on the stability of prices and economic activity over the next
several years. Under this policy, a central bank responds to stock prices, home values,
and other asset prices only insofar as they have implications for future output and
inflation over the medium term. Importantly, the strategy eschews any attempt to
influence the speculative component of asset prices, treating any perceived mis-pricing
as, rightly or wrongly, an essentially exogenous process. Following this strategy does not
imply that policymakers ignore the expected future evolution of speculative activity. If
policymakers suspect that a bubble is likely, say, to expand for a time before collapsing,
the implications of that possibility for future output and inflation need to be folded into
their deliberations. Practically speaking, however, I view our ability to act on such
suspicions as limited given how little we know about the dynamics of speculative
episodes.
Despite its approach to perceived speculative activity, the conventional strategy
does recognize that monetary policy has an important influence on asset prices--indeed,
this influence is at the heart of the transmission of policy decisions to real activity and
inflation. It occurs through standard arbitrage channels, such as the link between interest
rates and the discount factor used to value expected future earnings.

-3The second strategy, by comparison, is more activist and attempts to damp
speculative activity directly. It was described at length in "Asset Price Bubbles and
Monetary Policy," an article published by the ECB last year. I quote from the article:
"This approach amounts to a cautious policy of 'leaning against the wind' of an incipient
bubble. The central bank would adopt a somewhat tighter policy stance in the face of an
inflating asset market than it would otherwise allow if confronted with a similar
macroeconomic outlook under more normal market conditions. . .. It would thus
possibly tolerate a certain deviation from its price stability objective in the shorter term in
exchange for enhanced prospects of preserving price and economic stability in the
future." 2 I am labeling this second approach extra action, as it calls for steps that would
not be taken in ordinary circumstances. 3
Compared with the first approach, the extra-action strategy responds to a
perceived speculative boom with tighter monetary policy--and thus lower output and
inflation in the near term--with the expectation of significantly mitigating the potential
fallout from a possible future bursting of the bubble. Thus, the strategy seeks to trade off
the near-certainty of worse macroeconomic performance today for the chance of
disproportionally better performance in the future, on the theory that the repercussions of
a major market correction could be highly nonlinear. But the extra-action proposal is by
no means a bold call for central banks to prick market bubbles. As the ECB article
stresses, such an attempt would be extremely dangerous given the risk that a concerted
effort at stamping out a speculative boom would lead to outsized interest rate hikes and
recession. Rather, the extra-action strategy is intended only to provide some limited
insurance against the possibility of highly adverse events occurring down the road.

-4-

Common Ground

I will be talking at length about the differences between the two strategies, but I
must stress up front how much they have in common. Both policies aim to achieve the
same general objectives of monetary policy, using the same broad analytic framework.
Most central banks, I believe, share these basic features of monetary policymaking,
notwithstanding important differences in their official mandates and the nature of their
economies.
At the risk of considerable oversimplification, policymakers can be described as
seeking to set policy over time so as to minimize the present value of future deviations of
output from potential and inflation from a desired level. Of course, we may not be
prepared to write down a specific loss function and say, "There, that's what I'm
minimizing." But our deliberative processes and our actions seem broadly consistent
with that characterization of the general problem. This statement is true whether our
institutions have a specific mandate to keep inflation low and stable and output close to
potential, as in the United States, or whether our mandate is defined primarily in tenns of
stabilizing inflation, as in the euro area. Stabilizing output complements maintaining
price stability in the medium to long run, and often in the short run as well.
We also can agree that asset prices play critical and complicated roles in
detennining real activity and inflation--roles that may be changing over time because an
increasing share of wealth is market-detennined and easily liquified. Movements in
stock prices and real estate values affect household wealth and thus consumer spending.
Changes in bond prices, stock prices, and exchange rates imply movements in the cost of
capital and relative prices that influence investment and foreign trade; exchange rate

-5movements also directly affect the prices of goods and services. Finally, asset prices can
affect the value of collateral and thus the provision of credit, thereby influencing
aggregate spending. In cases of sharply falling market valuations, these adverse creditchannel effects may even be exacerbated by the deteriorating health of banks and other
financial institutions. In sum, asset prices influence the economy in complex and subtle
ways over potentially extended periods oftime.
Finally, I think it fair to say that most central banks, faced with only a limited
understanding of asset prices and their interactions with the full economy, engage in a
form of risk management when dealing with market booms and busts. In part, they do
this because any particular policy under consideration is never associated with a single
forecast for the future paths of output and inflation but, instead, with a large set of
possible scenarios with differing odds of coming to pass. While no one uses formal
Bayesian methods to solve this difficult problem, I think most policymakers do engage in
at least an informal weighing of the various possibilities and their implications when
setting policy.
Three Conditions for Extra Action to Lead to Better Outcomes

Now let me turn from areas of agreement to more contentious issues, ones that
have a strong bearing on the relative merits of the two strategies. As the ECB article
notes, extra action is often seen as a type of insurance. And as with any insurance policy,
before you buy you have to ask whether the expected benefits outweigh the costs. As I
see it, extra action pays only if three tough conditions are met. First, policymakers must
be able to identify bubbles in a timely fashion with reasonable confidence. Second, there
must be a fairly high probability that a modestly tighter policy will help to check the

-6-

further expansion of speculative activity. And finally, the expected improvement in
future economic performance that would result from a less expansive bubble must be
sizable. You may be thinking that, in stating the three conditions, I have slanted the case
with such phrases as "reasonable confidence" and "fairly high probability." But stick
with me, and I hope to persuade you that these probabilistic qualifiers are needed to judge
the merits of extra action.
For the moment, let me set aside the first condition and assume that central banks
can distinguish an emerging bubble from improving fundamentals at an early stage.
What about the other two conditions? Should we presume that a limited application of
restrictive policy would materially restrain the speculative boom and make its eventual
unwinding less disruptive for the overall economy?
Consider the U.S. stock market boom of the mid-to-Iate 1990s. The boom was
fueled by a sustained acceleration of productivity and an accompanying rise in corporate
profits--fundamental changes that justified a maj or rise in equity prices. How high those
prices should have risen was difficult to judge in real time because no one, not investors
or central bankers, could be sure how fast profits would grow in the future. In the event,
share prices increased more than was justified by improved fundamentals. But overly
optimistic expectations for long-run earnings growth were not being driven by easy
money, and I see no reason to believe that an extra 50 or even 100 basis points on the
funds rate would have had much of a damping effect on investor beliefs in the potential
profitability of emerging technologies. At present, we just do not have any empirical
evidence of a link between interest rates and corporate equity valuation errors, as
opposed to standard arbitrage effects.

-7In general, we have a very poor understanding of the forces driving speculative
bubbles and the role played by monetary policy. In fact, we cannot rule out perverse
effects. 4 Again, consider the u.s. experience of the late 1990s. When the FOMe
tightened in 1999 and early 2000, the trajectory of stock prices actually steepened, and
equity premiums fell--perhaps because investors became more confident that good
macroeconomic performance would be sustained. Since mid-2004, we have seen a
marked decline in bond-term premiums, even as the funds rate has risen steadily. These
episodes illustrate that risk premiums often move in mysterious ways, and we should not
count on the ability of monetary policy to nudge them in the intended direction.
Perhaps housing markets differ from equity and bond markets. For example,
homeowners, who may have a less sophisticated understanding of the economy than
professional investors, might mistakenly view a one-time rise in home prices--resulting,
say, from a decline in interest rates--as evidence of a more persistent upward trend. If so,
a monetary easing directed at stabilizing output and inflation might, conceivably, drive up
real estate values by more than fundamentals alone would merit. Still, you would expect
any mis-pricing from these sources to be reversed over time as interest rates returned to
normal. In any event, empirical evidence on this issue is scanty. More broadly, further
research into the causal connections, if any, between monetary policy and bubbles would
seem to be needed before we would know enough to be able to act on such linkages with
much confidence. 5
However, let us suppose a situation arises in which we are convinced that tighter
policy would check the future expansion of an emerging speculative bubble. Even then,
with the second condition now met, the third condition might not hold: The expected

~

8-

improvement in future macroeconomic performance from moderating the bubble's
expansion may not be enough to more than offset the up-front costs of extra action. To
explain this statement, I note again that extra action with near-certainty weakens the
economy and reduces inflation before the bubble bursts in exchange for the chance of
better macroeconomic performance in the future.
Admittedly, if the worst-outcome scenario associated with an unchecked bubble is
judged sufficiently dire and if the scenario is not seen as too improbable, then a riskaverse policymaker might regard the expected return from extra action insurance as worth
its upfront cost. However, our confidence in such an assessment would seem to hinge on
believing that the effects of market corrections could be markedly nonlinear. Proponents
of extra action often cite an increased risk of severe financial distress as a potential
source of such effects. However, without the onset of deflation, how large is this risk? In
recent history, the health of the U.S. financial system remained solid after the collapse of
the high-tech boom, despite the bankruptcy of dozens of telecom and dot-com firms, the
loss of more than $8 trillion in stock market wealth, and stress in the nonfinancial
corporate sector. Moreover, the financial sectors of most other developed economies also
weathered the worldwide drop in corporate equity values fairly well.
Of course, the nonlinear risks associated with a collapsing bubble may depend on
the initial health of the financial system, and under some circumstances we could be
worried about the potential for significant financial distress to accompany the bursting of
a bubble, should that bubble expand further. Even in such cases, however, I wonder
whether good prudential supervision in advance and prompt action to clean up any
lingering structural problems afterward would not be better ways to deal with this

-9-

•
possibility. Certainly, closer oversight of banking systems during the 1980s, including
the United States, would have left many economies in a stronger position during the early
1990s. This lesson has been absorbed by supervisory authorities around the world, as
evidenced by our successful efforts to strengthen bank capital and our financial systems.
I do agree that market corrections can have profoundly adverse consequences if
they lead to deflation, as illustrated by the United States after the 1929 stock market crash
and the more recent experience of Japan. But it does not follow that conventional
monetary policy cannot adequately deal with the threat of deflation by expeditiously
mopping up after the bubble collapses. In Japan, deflation could probably have been
avoided if the initial monetary response to the slump in real estate and stock market
values had been more aggressive; in addition, macroeconomic performance would have
been better if the government had dealt more promptly with the structural problems of the
banking sector. 6 As for the Great Depression, the Federal Reserve actually worsened the
situation by allowing the money supply to contract sharply in 1930 and 1931, after
unwisely attempting to prick the stock market bubble in the first place. Rather than
demonstrating the need for preemptive extra action to restrain emerging bubbles, these
examples are object lessons concerning the wisdom of central banks' easing promptly
and aggressively following market slumps when inflation is already low, so as to head off
the threat posed by the zero lower bound. By doing so, policymakers should be able to
avoid the severe nonlinear dynamics of deflation.
Proponents of extra action often argue that it should reduce the risk of hitting the
zero bound, but we should recognize that under some circumstances extra action may
actually exacerbate the problem. To see this, suppose that a speculative bubble has

- 10emerged and that a central bank, operating under a conventional strategy, has raised
interest rates to keep the projected output gap closed and expected inflation at its desired
level before the bubble bursts. Now the central bank contemplates taking extra action. In
a low-inflation environment, such a step would be a bad idea if, after averaging across all
the possible outcomes weighted by their likelihoods, the predicted moderation in the
bubble from tighter policy is small. In this case, the expected weakening in real activity
after the bubble bursts would be only marginally less severe under extra action, but
inflation would be substantially lower because the extra action policy would have
generated persistent economic slack beforehand. With inflation having already started
out at a low level, such a decline would be extremely dangerous because the zero bound
would now be much more likely to constrain monetary policy after the bubble bursts.
Under these conditions, extra action would therefore worsen expected economic
performance, not improve it.
Another pwported benefit of extra action is that, by raising the cost of capital to
firms and households, it helps reduce overinvestment fostered during speCUlative booms,
thereby making it easier for the economy to recover after the bubble collapses. However,
we should be careful not to exaggerate the macroeconomic importance of such capital
mis-allocation. True, the U.S. high-tech boom led to overinvestment in some sectors,
wasting resources and creating lingering difficulties while capital overhangs were
eliminated. But it is hard to see much of a cost in terms of diminished aggregate
productivity, given the robust growth of output per hour over the past few years.
Furthermore, even if tighter monetary policy would have damped the enthusiasm
for dot-com firms in the late 1990s, higher interest rates would have also led to less

•

- 11 -

housing and less business investment outside the high-tech sector, where valuations were
not obviously out ofline with fundamentals. Thus, mitigating capital misallocation in
one sector would have created capital misallocations elsewhere, making the assessment
of the net gain from extra action difficult. And, as I have been pointing out, extra action
would have idled some capital entirely for a time as economic activity fell short of its
level consistent with stable inflation.
Now I would like to return to the first condition, the one I sidestepped a few
minutes ago--the question of identifying market bubbles in a timely fashion. The EeB
article stressed that such identification is a tricky proposition because not all the
fundamental factors driving asset prices are directly observable, as the productivity
acceleration and stock market boom of the 1990s illustrate. For this reason, any
judgment by a central bank that stocks or homes are overpriced is inherently highly
uncertain.
Under extra action, mistakenly identifying a bubble has significant costs. By
acting to mitigate a nonexistent problem, the central bank reduces real economic activity
and inflation below their desired levels to no purpose. Admittedly, policymakers, once
they recognize their mistake, would presumably want the economy to run hotter for a
time to restore the previous rate of inflation and would thereby make up for the initial
output losses. But coming to the realization that the original assessment was mistaken
and that asset prices were in line with fundamentals is likely to take some time. And the
mistaken call would have reduced welfare by needlessly inducing fluctuations in the
macro economy.

- 12Timing is also an issue. Let us suppose that the evidence is so compelling that
policymakers become fairly confident that valuations are excessively rich.
Unfortunately, I suspect that this call would often come so late in the day that, given the
lags in the monetary transmission mechanism and uncertainty about the duration of .
bubbles, raising interest rates might actually risk exacerbating instability. The market
correction could occur with policy in a tighter position but before extra action had enough
time to materially influence speculative activity.
Notwithstanding the controversial aspects of identifying bubbles, policymakers
may still want to warn the public about the possibility of asset price misalignments when
the evidence merits. Such talk might do some good by prompting investors to stop and
rethink their assumptions. And talk by itself should not do much lasting harm even if
valuations turn out to be justified--provided, however, that words are not seen as
precursors to action under circumstances in which conventional policy would still be the
best approach.
To wrap up this critique, I summarize as follows: Ifwe can identify bubbles
quickly and accurately, are reasonably confident that tighter policy would materially
check their expansion, and believe that severe market corrections have significant nonlinear adverse effects on the economy, then extra action may well be merited. But if even
one ofthese tough conditions is not met, then extra action would be more likely to lead to
worse macroeconomic performance over time than that achievable with conventional
policies that deal expeditiously with the effects of the unwinding of the bubbles when
they occur. For my part, I am dubious that any central banker knows enough about the
economy to overcome these hurdles. However, I would not want to rule out the

..
- 13 -

•

possibility that in some circumstances, or perhaps at some point in the future when our
understanding of asset markets and the economy has increased, such a course of action
would be appropriate.

Asymmetries and Moral Hazard
Proponents of extra action have their own bones to pick with the conventional
strategy, especially as it relates to the alleged asymmetric nature of the policy's response
to asset market booms and busts. In particular, the claim is often made that, based on the
FOMC's actions over the past twenty years, the Fed actively works to support the
economy in an event of a sharp decline in asset markets but does little or nothing to
restrain markets when prices are rising, thereby creating moral hazard problems.
This argument strikes me as a misreading of history. U.S. monetary policy has
responded symmetrically to the implications of asset-price movements for actual and
projected developments in output and inflation, consistent with its mandate. The most
convincing evidence for this statement can be found in the results: Interest rates have
been consistent with underlying inflation remaining reasonably stable for some time now,
accompanied by relatively mild fluctuations in real activity. 7
Conventional policy as practiced by the Federal Reserve has not insulated
investors from downside risk. Whatever might have once been thought about the
existence of a "Greenspan put," stock market investors could not have endured the
experience of the last five years in the United States and concluded that they were hedged
on the downside by asymmetric monetary policy. Nor, for that matter, should they have
concluded that the Federal Reserve does not act on the upside: If asset prices had been
more closely aligned with fundamentals in the late 1990s, our policy would almost

- 14certainly have been easier, all else equal, because aggregate demand would have been
weaker and hence inflation pressures even more muted than they were. The same
considerations apply to homeowners: All else being equal, interest rates are higher now
than they would be were real estate valuations less lofty; and ifreal estate prices begin to
erode, homeowners should not expect to see all the gains of recent years preserved by
monetary policy actions. Our actions will continue to be keyed to macroeconomic
stability, not the stability of asset prices themselves.
Ironically, one can argue that extra action may pose a more significant risk of
moral hazard. It is one thing for policymakers to raise questions about the relationship of
asset prices to fundamentals and another for a central bank to take action to influence
valuations in the direction of some "appropriate" level. How does this strategy play out if
a central bank takes extra action and speculative activity continues unabated or even
intensifies? Do policymakers raise rates even further above levels consistent with
conventional policy and, if so, at what consequences for the economy? And what is the
risk that, in taking such steps, a central bank would be seen by investors as taking on
partial responsibility for asset prices? If so, would the pressure on central banks to
support asset prices in market downturns increase?
Conclusion

My remarks today have been intended as a salute to Otmar and to all the valuable
contributions he has made over the years to my thinking and to that of policymakers
around the world. Otmar, you have taught me much about intellectual rigor in support of
central bank contributions to economic welfare--and about friendship. Weighing the
relative merits of extra action and conventional policy is not easy and requires a nuanced

.
- 15 -

interpretation of the arguments and the evidence, as well as some hard thinking. Otmar
and his colleagues have done this in advancing the case for extra action, and by so doing
they have given me a good intellectual workout--and Otmar, I thank you for that. I hope
my response has provided a good workout in return. I look forward to continuing the
debate and especially the friendship for many years to come.

I David Reifschneider, of the Federal Reserve Board's staff, contributed substantially to the preparation of
these remarks.

European Central Bank (2005), "Asset Price Bubbles and Monetary Policy," Monthly Bulletin (April), p.
58.

2

The article's label for this strategy--Ieaning against the wind--has been used for many years to describe
the standard behavior of central banks. Given this history, I think that using the term extra action is less
confusing.
3

4 From a theoretical standpoint, the "rational bubble" literature demonstrates how a rise in interest rates
might lead rational agents to boost the growth rate of asset prices during a speculative episode.
5 Recently, ECB staff economists Carsten Oetken and Frank Smets have taken a laudable first step at
addressing this issue in a paper that establishes some of the basic empirical facts about the correlations
among interest rates, money, credit, asset prices, fmancial distress, and macroeconomic performance. See
Carsten Detken and Frank Smets (2004) "Asset Price Booms and Monetary Policy," European Central
Bank Working Paper Series 364, (Frankfurt: ECB, May).

See Alan G. Ahearne, Joseph E. Gagnon, Jane Haltmaier, and Steven B. Kamin (2002), "Preventing
Deflation: Lessons from Japan's Experience in the 1990s," International Finance Discussion Paper Series
2002-729 (Washington: Board of Governors of the Federal Reserve System, June).

6

As evidence of asymmetry, observers often cite Claudio E.V. Borio and Philip Lowe (2004), "Securing
Sustainable Price Stability: Should Credit Come Back from the Wilderness?" Bank of International
Settlements Working Paper 157 (Basel: BIS, July). The authors purport to show that the federal funds rate
was unusually low during the headwinds period of the early 1990s but not correspondingly high before the
onset of the 1990 recession. But their assessment is made in relation to the Taylor rule, which is not a
particularly good description of monetary policy during this period of opportunistic disinflation. In the
event, inflation in the United States came down steadily over the first half of the 1990s, accompanied by
significant economic slack--results that seem to belie the claim that policy was overly easy.
7