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Inversion
Global Interdependence Center
Central Bank Series
Federal Reserve Bank of Philadelphia
Philadelphia, Pennsylvania
May 18, 2006

I

nversion has been much in the news for
some months now. Indeed, inversion has
made the big time, with William Safire
devoting a column in the Sunday New
York Times (April 23, 2006) to IYC—inverted
yield curve. By inversion, of course, I’m referring to a situation in which short-term interest
rates are higher than long-term interest rates.
When I agreed to speak on this topic last fall,
market concern over IYC was running high.
The FOMC had been providing guidance that it
would probably continue to raise the target federal
funds rate; given the level of the 10-year Treasury
yield in the 4¼ to 4½ percent range, market
observers expected that the funds rate would soon
be above the 10-year rate. Recession concerns
were widely discussed, because in the past IYC
has often been associated with recession. Moreover, many found it odd that until last month the
monthly average 10-year bond rate was actually
lower than it had been in June 2004, when the
FOMC began to raise the fed funds rate target. It
seemed a puzzle that the 10-year rate was actually
the same in March 2006 as it had been in June
2004, even though the FOMC had raised the target
fed funds rate from 1 percent to 4¾ percent. Now
that the 10-year rate has risen by another 50 to
75 basis points, to about 5.15 percent, apparently
everyone feels a lot better!
For simplicity, using monthly average data,
except where indicated otherwise, I’ll concentrate
on the difference between the 10-year constantmaturity Treasury yield and the federal funds
rate. Some analysts this past winter called attention to an inversion between the 1- or 2-year rate

and the 10-year rate, but looking for some particular part of the yield curve where a shorter rate
is above a longer rate is scratching for a story.
Surely, no important issue can depend on an
inversion somewhere along the yield curve of a
few basis points.
Before proceeding, I want to emphasize that
the views I express here are mine and do not
necessarily reflect official positions of the Federal
Reserve System. I thank my colleagues at the
Federal Reserve Bank of St. Louis—especially
Michael Dueker—for their assistance and comments, but I retain full responsibility for errors.

TERM-STRUCTURE THEORY
An important problem with much IYC commentary is that it involves a search for patterns
in the data without an effort to understand the
economics that might lie behind the patterns.
Understanding why observations follow a particular pattern is essential to judging whether a pattern
is likely to persist or apply to today’s situation.
Economists have been studying the term
structure of interest rates for a long time. The
first proposition is that a long interest rate reflects
investor expectations of the average short rate
over the horizon of the long rate. Thus, today’s
1-year rate reflects expectations of the next 52 1week rates; today’s 10-year rate reflects expectations of the next 10 1-year rates.
I deliberately used the phrase “reflects
expectations” because there is ample evidence
that a long rate is not always equal to the appro1

FINANCIAL MARKETS

priately weighted average of the short rates over
the horizon of the long rate. Most of the time, long
rates are somewhat above short rates. Over the
past 50 years, for example, the 10-year Treasury
rate has averaged about 90 basis points above the
federal funds rate. The difference between the
long rate and average expected short rate over
the horizon of the long security is called the
“term premium.”
On average, the term premium is positive,
but theory does not predict any particular relationship. The term premium is thought to arise
from investor attitudes toward risk. Capital values
fluctuate more the longer a bond’s maturity, and
investors averse to capital risk therefore prefer
shorter maturities. On the other hand, interest
income fluctuates more for a series of investments
in short-term bonds than for a long-term bond;
investors averse to income instability therefore
prefer longer-term bonds.
The balance of investors with different and
changing attitudes toward risk changes over time,
and other conditions may also change. Thus,
there is no reason to expect that term premiums
will be constant, and they aren’t. Given that
investor expectations about future short rates are
not directly observable, and their preferences
that create term premiums are not directly observable either, there is no absolutely reliable way to
disentangle changing interest rate expectations
from changing term premiums.

SOME HISTORY
Many of the inversions of the yield curve
starting in the 1960s occurred under the old
deposit interest rate ceilings established under
Regulation Q. The ceiling on the deposit rate led
to “disintermediation” from the banking system
when monetary policy tightened and increased
the responsiveness of the quantity of money inside
the banking system to Federal Reserve policy
actions. However, there was no inversion associ1

2

ated with the recessions of 1957-58 and 1960-61.
Before the mid-1960s, the Fed adjusted Regulation
Q interest ceilings in a fashion timely enough to
prevent significant disintermediation.
In an environment of slow adjustment of Reg
Q ceilings, when the Fed stepped on the monetary
brakes, bank credit became tight and the real
short-term interest rate quickly rose well above
its equilibrium level. Because the market anticipated that the monetary brakes would be loosened
within a relatively short time frame, long-term
interest rates rose by a much smaller amount,
and the yield curve inverted temporarily. It was
during this era that yield-curve inversions came
to carry negative business-cycle connotations.
All too often, the clampdown on credit was
severe enough to be associated with a recession
but not steadfast enough to bring about lasting
disinflation.
Fortunately, since the early 1980s, three
things have changed for the better. First, lasting
disinflation was achieved in the VolckerGreenspan era. Second, financial deregulation
did away with Regulation Q, and important financial innovations, such as hedging instruments,
have lessened the economic fallout from shocks.
Third, the economy itself has become more stable—a phenomenon known as the “Great
Moderation.” Moreover, these positive developments reinforce each other because, as Chairman
Bernanke has noted in Congressional testimony,
a more stable environment provides monetary
policymakers greater latitude to respond aggressively to shocks.1 It was this latitude that permitted the Federal Reserve to maintain the federal
funds rate at 1 percent from June 2003 to June
2004 while waiting patiently for the current
expansion to establish firm legs.

IYC AS RECESSION PREDICTOR
One quip about the predictive power of yield
curve inversions is that they have predicted six

Testimony of Chairman Ben S. Bernanke, Semiannual Monetary Policy Report to the Congress before the Committee on Financial Services,
U.S. House of Representatives, February 15, 2006.

Inversion

of the last four recessions. In fact, starting in the
mid-1960s, there have been nine notable inversions of the yield curve and six business recessions. The historical record of yield curve
inversions, recessions, and false alarms reveals
several regularities. Such an analysis also sheds
light on today’s relatively flat yield curve.
The basic proposition is that the yield curve
reflects investor expectations of future interest
rates. These expectations depend on anticipated
Fed policy adjustments, which in turn reflect
expected developments in the real economy and
the rate of inflation. Consider a classic episode
to illustrate the process. Inflation began to rise
persistently in 1967 and, after the middle of the
year, the Fed began to tighten policy. In response
to tighter fiscal policy enacted in mid-1968, which
many believed would cool the economy, the Fed
eased policy a bit. However, the economy did
not slow and inflation continued to worsen. The
FOMC then raised the fed funds rate almost every
month. The yield curve had inverted slightly in
the spring of 1968, and the inversion deepened
as the Fed tightened policy. In August 1969, the
peak month for the funds rate, the inversion
reached its maximum extent of 250 basis points.
The business cycle peak was December. Not until
March 1970 did the Fed ease policy enough to
bring the funds rate down significantly.
The basic story, as I see it, was that the Fed
was slow to ease policy in 1969 and 1970 because
it was concerned about the inflation rate. The
bond market could see that the economy was
weakening and that rates would be coming down,
which is why the inversion developed. But the
Fed did not want to ease policy until inflation
slowed, both because it wanted to maintain downward pressure on the inflation rate and because
it was concerned that premature easing would
raise inflation expectations. This same pattern
played out in spades in the months around the
November 1973 business cycle peak. Inflation
was much higher and inflation expectations more
entrenched. Using monthly average data, the peak
fed funds rate was in July 1974 and the inversion
that month was over 500 basis points. The economy weakened dramatically in the second half

of 1974, and the Fed eased policy. The inversion
lasted through December.
The story around the cycle peak in March
2001 was a bit different. The Fed maintained a
target for the funds rate of 6.5 percent starting in
mid-May 2000. After May, the 10-year Treasury
rate fell a bit and the yield curve inverted. The
inversion reached a maximum of 116 basis points
in December. Policy in 2000 was dominated by
concern over the threat of inflation rather than
actual inflation. The FOMC began to cut the funds
rate target in January 2001, ahead of the cycle
peak in March. The inversion ended in April as
the Fed cut the funds rate target aggressively.
While it is true that an inversion preceded the
cycle peak, it is also true that the FOMC began to
cut rates before the cycle peak and indeed cut
aggressively because inflation was controlled.
Now that I’ve reviewed a few episodes, let’s
try to generalize a bit. Using weekly average data
to tie down timing relationships accurately, the
last date on which the yield curve is inverted by
at least 100 basis points can be considered the
date on which the inversion ebbs and starts to
tail off. We’ll call this date the “ebb date.” One
interesting pattern across yield curve inversions
is that the long rate typically rises, although sometimes only slightly, in the three months prior to
the start of the inversion and then falls in the
three months prior to the ebb date. It is not obvious that the long rate would be falling as the
inversion is declining, but this pattern held in
many of the inversions that preceded or coincided
with recessions—specifically the inversions that
started in 1968, 1973, 1978, 1982, 1989, and 2000.
These cases fit the scenario whereby monetary
policy initially tightens enough to lift all interest
rates, including long-term rates, but a weakening
economy and market anticipations of Fed easing
subsequently lead to declines in long-term rates.
The inversion ebbs because the Fed sees the
weakening economy and brings the funds rate
down, and the funds rate declines more quickly
than does the long rate.
It is also worth noting that in all six of these
classic instances where an inversion of the yield
curve preceded a recession, the real federal funds
3

FINANCIAL MARKETS

rate—measured as the difference between the
federal funds rate and core PCE inflation—
exceeded 4 percent and sometimes by a wide
margin. These were episodes of substantial policy
restraint, motivated by inflation or the threat of
inflation.
There are three false alarm cases where no
recession ensued—the inversions that began in
1966, 1995, and 1998. In none of these cases did
the inversion reach 100 basis points using monthly
average data. In the false alarm cases, the real
federal funds rate was at or somewhat below 3
percent.
The anomaly among the inversions, in that it
is neither one of the classic cases nor a false alarm,
is the inversion that started in October 1980. The
ebb date of this inversion, in September 1981,
occurred in rather unusual circumstances. The
economy had gone back into recession in July
1981 and the 10-year rate was near its post-war
high of about 15½ percent at the height of the
Fed’s struggle to bring inflation down. Although
by September 1981 the fed funds rate had come
down from its peak earlier in the year, the policy
outlook was extremely uncertain because the
inflation outlook was so uncertain. As it turned
out, the economy weakened rapidly as the recession took hold and both long and short rates
declined after September 1981. The inversion
disappeared as short rates declined more quickly
than long rates, but then reappeared for a few
months in 1982.
Analyzing the current situation in light of
these patterns, using weekly average data, the
spread between the 10-year Treasury and the
federal funds rate never became negative this past
winter, though it came close to zero in January
and February. The real federal funds rate has
remained below 3 percent in all of 2006. Thus,
the recent relatively flat yield curve has much
more in common with the cases where yield curve
inversions were not followed by a recession.
One lesson from these episodes is that the
yield curve must be combined with additional
information in order for a reliable recession signal
to emerge. In particular, the term spread should
be considered jointly with the level of the real
4

short-term interest rate when gauging whether
recession is likely.
As a recession predictor, yield-curve inversions do not outperform other simple rules of
thumb, such as troughs in the unemployment
rate. Even though the unemployment rate is
widely known as a lagging economic indicator, a
simple predictive rule is that a rise from a trough
level in the unemployment rate by at least 0.3
percentage points lasting at least three months
occurs prior to every cycle peak. For example,
by August 2000, the unemployment rate had
risen 0.3 percentage points above an April 2000
trough rate of 3.8 percent. The recession then
began seven months later in March 2001. Nevertheless, the eight correct signals from the unemployment rate are accompanied by three false
alarms—with the latest in February 1986. This
ratio of hits to misses is similar to the ratio for
yield curve inversions. Undoubtedly, we could
find many other recession signals that would
match the record of inverted yield curves. That
all these supposed signals are of limited value is
indicated by the fact that forecasters do not have
a stellar record of forecasting recessions. If the
signals were clear, forecasting would be easy. It
is not.
I haven’t attempted a citation count to determine when inversion aversion reached its peak
intensity, but the discussion was certainly active
from late last fall to early this year. Perhaps what
triggered this discussion was that, while the FOMC
was raising the target fed funds rate starting in
June 2004, the 10-year rate traded most of the time
in a range from 4 to 4.5 percent. Last fall, as the
target funds continued to rise but the 10-year
rate did not, it appeared only a matter of time
until the inversion would occur. In fact, using
monthly average data, we have not had an inversion through April 2006.
The key to understanding this situation is
that increases in the target funds rate were well
predicted in June 2004, when the increases began
from the unusually low federal funds rate of 1 percent. In June 2004, the market correctly gauged
that the Fed would raise the funds rate steadily
and gradually for the next year and a half. Not

Inversion

until the November 2005 FOMC meeting did the
target funds rate exceed the rate that had been
expected in June 2004. With the funds rate rising
on the expected track, there was no reason for the
10-year bond rate to depart in any major way from
its level in June 2004. The increase in the bond
yield since November 2005 is consistent with the
idea that the funds rate has now increased somewhat more than the market anticipated earlier.
Why did rates behave so much the same as
expected in June 2004? The most important reason is that the economy came in so close to what
had been forecast. Going as far back as January
2004, the Blue Chip forecasters maintained very
steady and accurate forecasts of 2005 GDP growth,
which came in at 3.5 percent. The main surprise
was in the inflation rate. In turn, that surprise
was a consequence of energy prices, which have
increased far beyond levels predicted in June
2004 but even today have not much affected core
inflation. What has happened to raise the expected
path for the target federal funds rate from expectations in place late last year, and therefore has
also affected longer-term rates, is the persistence
of energy price increases. In January 2005, the
Blue Chip consensus for CPI inflation for 2006
was 2.3 percent. As of the May 2006 Blue Chip
release, that consensus is now up to 3.1 percent;
much of this increase took place after Hurricane
Katrina.
Unless we experience significant departures
from the expected course for the economy, the
recent rise in the 10-year Treasury yield from
about 4.6 percent in February to about 5.15 percent today has done much to diminish the likelihood of a substantial inversion in the yield curve
in the near future.

RECENT BEHAVIOR OF LONGTERM RATES AND THE TERM
PREMIUM
I’ve emphasized the importance of interest
rate expectations for shaping the yield curve and
believe that the rate expectations story explains

most of what we’ve observed. But there are no
doubt other forces at work. It appears that the
term premium in long rates fell as the funds rate
target increased. One likely reason that the term
premium fell in the first year and a half of this
tightening cycle is that the market understood
the path that short-term interest rates would take
in the tightening cycle that began in late June
2004. That predictability reduced the risk of
holding longer-term bonds.
Market commentary has attributed much of
the recent increase in long rates to a restoration
of a more-normal term premium for holding longterm debt. But policymakers should not view the
term premium as a single component of long-term
interest rates. Instead, the term premium consists
of compensation for the risk that real interest rates
will turn out to be higher than expected in the
future and separate compensation for the risk
that inflation will turn out to be higher than currently expected. Naturally, if the term premium
increases because of changes in bearing real
interest rate risk, as a policymaker I am more
comfortable with that than if the term premium
increases because of market concerns about the
risk of inflation. Yields on Treasury inflationindexed securities, combined with factor models
of the term structure of interest rates, suggest that
the compensation for bearing real interest-risk
dropped between June 2004 and late 2005,
although it has rebounded somewhat since then.
Because some of these factor models suggested
that the term premium had dipped nearly to zero
by late 2005, some rebound was likely.
Among the international factors cited as
influences on U.S. interest rates in the past few
years is the global saving glut. Unusually high
saving might hold down the level of real interest
rates, but there is no reason why there should be
an effect on the shape of the term structure. In
any event, it appears that real interest rates are
returning to a more normal level in the United
States. The 10-year indexed bond had a rate of
about 1.6 percent in the fall of 2004; that rate is
now up to about 2.4 percent.
5

FINANCIAL MARKETS

FORWARD RATES
Although the yield curve is an imperfect
recession predictor, the term structure of interest
rates provides very useful glimpses of what shortterm interest rates are likely to be in the future.
A forward interest rate far enough into the future,
say nine years ahead, provides information
about the trend rate of inflation markets expect.
Measures of expected inflation in the short run,
say in the next two years or so, reflect energy
price shocks, for example, that will not influence
the long-run trend rate of inflation. Similarly, no
one can forecast the state of the business cycle
nine years into the future, so the implied far forward rate reflects neutral business cycle conditions. For this reason, a clear shift up or down of
the implied far forward rate suggests that either
the trend level of expected inflation has changed
or the market’s inference of the trend real rate of
return has been altered. In principle, one could
use data on stripped inflation-indexed bonds to
infer the implied forward real rate, but trading in
this market is somewhat thin. Nevertheless, the
implied far forward real rate is not expected to
undergo sudden changes. Hence we can interpret,
as a good approximation, changes in the implied
far forward nominal rate as a combination of
changes in long-term inflation expectations and
in the term premium.
Price data from stripped Treasury bond coupons
show that the implied far forward one-year rate
nine years in the future has fallen since the Fed
initiated its tightening cycle in June 2004. In that
time span the implied forward rate has fallen
from about 61/8 percent to about 5½ percent. Thus,
the signal from the Treasury bond market is that
the Fed’s measured but steady pace of removing
policy accommodation has been sufficient to
keep long-term inflation expectations and risk
premia well-contained.

CONCLUDING COMMENTS
I must say that I’ve been a bit puzzled by the
inversion/recession talk that began last fall. As
6

already noted, the spread between the 10-year
bond and the fed funds never became negative
last fall and still isn’t. Yet, inversions associated
with recessions have been quite large. Using
monthly average data, the 1969 inversion reached
250 basis points; the 1974 inversion exceeded
500 basis points; the 1980 and 1981 inversions
exceeded 600 basis points. Milder inversions
seem to have been associated with milder recessions. The 1989 inversion reached 125 basis
points and the 2000 inversion reached 116 basis
points. We never got close to any of these last
fall. Finally, looking back at 1980-82 experience
makes clear that simply counting presumed patterns in the data, without guidance from economic theory, is not a wise strategy. The early
1980s were so different from today’s conditions
in so many respects that the experience of twin
recessions in a high inflation era has little bearing on understanding the term structure today.
The term structure of interest rates provides
a window into investor interest rate expectations.
It is always worthwhile for policymakers to consider those expectations but not wise to take them
at face value without further analysis. Interestrate expectations reflect investor understanding
of how rates will evolve, which is why an inverted
yield curve has often preceded business cycle
peaks. But the market’s rate expectations also
depend importantly on the market’s read of what
the FOMC will do. If the market’s expectation
does not match the FOMC’s own expectation, then
policymakers need to do some soul searching.
There are two possibilities: either the market
may have a better understanding of where the
FOMC is likely to take policy than the FOMC
does, or the market may be misreading the FOMC’s
intentions.
Arguably, the market was ahead of the FOMC
in 2000; the peak for the 10-year rate was 6.66
percent in January, and by December the rate
was down to 5.24 percent. As evidence of the
economy’s weakening accumulated, the FOMC
first cut the fed funds rate target in January 2001.
Conversely, after the FOMC lowered the funds
rate target to 1 percent in June 2003, the market
seemed primed to expect that the Committee

Inversion

would soon be raising the rate. To better align
market expectations with its own, in its August
2003 meeting the FOMC introduced language in
its statement indicating that “the Committee
believes that policy accommodation can be maintained for a considerable period.”
At least as of today, the market’s concerns
last fall that the yield curve would invert and
signal a recession seem to have evaporated. There
is no obvious misalignment of market interest
rate expectations and the likely course of policy
given information available today. What I believe
will happen is that FOMC policy decisions and
market expectations will evolve as newly arriving
data either change, or affirm, the current outlook
for the economy. The policy statement following
the FOMC’s meeting of May 10 indicated the
Committee’s view that economic growth was on
a solid, but moderating, track and that inflation
was contained, but still a risk.
The Committee also emphasized that future
policy would depend on how arriving information affected the economic outlook. I myself place
great emphasis on this point. Experience indicates
that economic forecasts are not especially accurate, and that means that monetary policy actions
should depend on how the outlook changes with
new information rather than be decided in
advance based on the forecast.
I hope I’ve provoked you sufficiently that
you’ll ask some questions. Fire away.

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