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Inflation Signals and Inflation Noise
University of Arkansas at Little Rock
Peabody Hotel
Little Rock, Arkansas
April 6, 2004

T

he employment report for March,
released last Friday and showing a jobs
gain of 308,000 over February, was
certainly good news. Everyone hopes
that monthly reports over the rest of this year
and for years to come will also bring good news
on the employment front.
Assuming that employment gains continue,
market focus will naturally shift from employment
to concerns over inflation risks. Indeed, some
market commentary already has shifted in that
direction. My purpose today is to provide my
perspective on the problem policymakers face in
determining when inflation risks are rising.
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 for their comments; Robert H. Rasche, senior vice president
and director of Research, provided special assistance. However, I retain full responsibility for
errors.

BACKGROUND
In the four decades since the beginning of the
Great Inflation of the 1960s and 70s, economists
and central bankers have acquired a much better
understanding of the source and consequences
of inflation. When the Great Inflation began, it
was common to cite one or another idiosyncratic
events as the driving force behind the observed
change in prices: OPEC, steel prices, anchovies
and forth. Anchovies? Few today will understand

this reference, so I’ll have to explain that some
analysts argued that the disappearance of
anchovies from the coast of Peru in 1972 had
something to do with rising inflation in 1973.
Today, however, economists universally accept
the proposition that sustained inflation or deflation is, in the words of Milton Friedman, “everywhere and always a monetary phenomenon.”
The experience of the Great Inflation brought
home to the public and policymakers alike the
burden that inflation imposes on an economy.
In the absence of institutions adapted to an inflationary environment, the efficiency of market
prices to signal the relative scarcity of goods and
services is impaired. Incomes and wealth are redistributed capriciously, even when the inflation is
partially foreseen, in a tax system that is not fully
indexed. Regulations on nominal interest rates,
such as deposit ceilings and usury laws, interact
with the inflation rate to distort demand in certain
sectors such as housing. Some financial institutions, such as the thrifts that specialized in housing finance, were driven towards extinction. It is
possible, though the evidence is not conclusive,
that even modest sustained inflation negatively
impacts the rate of growth of labor productivity.
Central bankers world-wide have taken these
lessons to heart. Since the initial inflation targeting experiment by the Reserve Bank of New
Zealand in 1990, thought at the time to be radical,
inflation targeting has become the stated objective
of at least 11 central banks, including those of
developed and developing countries. These central banks publish either a numeric value, or a
range of values, to which they commit as an infla1

MONETARY POLICY AND INFLATION

tion policy objective over some time horizon. For
most of these central banks, achieving the inflation target is, under normal market conditions,
the single policy objective. For these policymakers, the idea, embodied in the original Phillips
curve analyses, that it is possible to permanently
trade-off a lower unemployment rate or a higher
level of real output for a higher rate of inflation
has been relegated to the textbooks on the history
of economic thought.
Other central banks, including the Federal
Reserve, have declined to quantify their inflation
objective. Nevertheless, most, if not all of these
institutions acknowledge their primary responsibility to produce a low and stable inflation
environment. In the case of the Federal Reserve,
the FOMC has stated as its policy objective to
achieve price stability in order to achieve maximum sustainable economic growth, thereby fulfilling its dual legislated mandate under the
Humphrey-Hawkins Act.
The FOMC has never defined “price stability”
numerically, but its commitment to price stability
is not in doubt. I have indicated on several occasions that my own inflation target is zero, properly
measured. Because all our measures of inflation
have some upward bias, my definition of price
stability is consistent with a small positive measured rate of inflation. Our recent inflation experience is, I believe, a good approximation of price
stability.
The policy problem faced by the FOMC, and
many other central bankers, today is significantly
different from that 25 years ago. By the late 1970s,
the inflation rate in the United States had become
unacceptably high—both for the FOMC and for
the public in general. There was disagreement in
the economics profession as to whether the costs
of disinflationary monetary policy were worth
bearing, but the FOMC concluded that a more
disciplined monetary policy was necessary. The
decisive date was October 6, 1979, when the
FOMC decided to adopt the “New Operating
Procedures.” Subsequently, the FOMC permitted
the federal funds rate to exceed 20 percent. With
the tighter monetary policy and changing inflation
2

expectations in the market, the economy experienced a severe recession in 1981-82.
Measuring inflation by 12-month changes in
the consumer price index (CPI), inflation fell from
a peak of 13.3 percent in 1979 to 3.8 percent in
1982, and remained in the neighborhood of 4
percent into the mid 1980s. Inflation rose a bit in
the late 1980s, and reached 6.1 percent in 1990,
in the face of the oil shock that accompanied
Iraq’s invasion of Kuwait.
In the early 1990s, the consensus was that
the economy had not returned to price stability.
Any substantial risk that inflation might rise was
clearly undesirable and necessitated a policy
response. But over the course of the 1990s, inflation was flat to gradually falling, and with further
declines in the early part of this decade most
observers concluded that the battle for price stability had been won.
Policy discussions today must consider twosided outcomes—the risks to price stability are
symmetric. A significant breakout of inflation
above our current situation is certainly not desirable—no one wants to throw away the hard-earned
accomplishments of the past 25 years. However,
a significant decline in inflation from current rates
may not be desirable either—no one wants to
replicate the deflationary experiences of the 1930s
or Japan’s experience in the 1990s. The consensus
of the FOMC, as reflected in the most recent press
release, is that the upside and downside risks to
inflation are almost balanced.
When the primary battle against inflation
started in 1979, there was a strong case for paying
great attention to the rate of money growth as a
measure of the thrust of monetary policy. Money
growth is not irrelevant to assessing inflation risks
today, but the emphasis has changed. For a variety
of reasons, and especially because expectations
of low inflation are so entrenched in the markets,
short-run money growth is an inadequate indicator for monetary policy purposes. What we need
to do instead is to extract as best we can evidence
of possible inflationary pressures from a variety
of other sources of information.

Inflation Signals and Inflation Noise

TRANSITORY AND PERMANENT
CHANGES IN PRICES
How can we best read the “news” in the price
data that become available every month? The
problem is to uncover information that might
indicate that a higher rate of sustained inflation
could be at hand. The FOMC should respond to
the signal and not to the noise in the data. Separating inflation signals from inflation noise is a
serious challenge.
Throughout most of the post-World War II
history in the United States, inflation has been a
highly persistent process. Nevertheless there is a
lot of random month-to-month variation in the
measured price indexes. It is this non-systematic
variation that we call “noise.” Somehow, policymakers have to look through the “noise” to discern
the signal about the underlying trend in inflation
in order to formulate appropriate policy actions.
This signal extraction problem is the rationale
for the development of a number of supplementary measures of inflation, beyond the broad-based
price indexes collected by the government statistical agencies. In particular, in addition to the CPI
and personal consumption price index, “core”
measures of inflation that exclude food and energy
prices are often highlighted.
In monetary policy reports to Congress, congressional testimony, and public speeches,
Chairman Greenspan and other members of the
FOMC have focused on the core measure of the
personal consumption price index. The rationale
for the construction of the core measures of inflation is not that food and energy are unimportant
items of household consumption. The core measures came to prominence in the 1970s when food
and energy prices were extremely volatile. Under
those conditions the core inflation measures likely
provided helpful filters through which to discern
a signal of the inflation trend. Removing these
components removes a source of short-run noise
that can obscure underlying price developments.
Another approach to identifying the signal is
the median CPI index. The Federal Reserve Bank
1

of Cleveland publishes such an index.1 The
median CPI, by construction, will exclude any
CPI component price index that is highly volatile
in the short run, as this component inflation rate
will typically appear in one of the tails of the
cross-section dispersion of the inflation rates of
the CPI components.
I must confess that I am uncomfortable with
arbitrarily defined filters. Filtering of transitory
shocks where the shocks are understood and can
be identified is clearly appropriate. An example
is the increase in tobacco prices following the
legal settlement with the major tobacco companies several years ago. It was well understood
that this was a one-time increase in tobacco prices
that would finance the funds established as part
of the settlement. It was possible to estimate the
impact of those price changes on the overall CPI
and most economists filtered this impact out in
order to assess the inflation signal at the time.
Absent specific information on which to
base estimates of “inflation noise,” care must be
taken to assure that the techniques used to filter
transitory inflation are robust. The late Karl
Brunner used to criticize the “upper tail theory
of inflation”—that inflation is caused by the
increases in the prices of those items that happened to be rising the fastest at any point in time.
If these “upper tail” rates of inflation are filtered
out of the inflation measure, then there can be
no inflation! Clearly arbitrary filtering can be used
to define away substantive problems. I believe
that additional research into defining and
extracting inflation trends has the potential to
provide valuable insights to monetary policymakers.
Though the evidence suggests that U.S. inflation in the second half of the twentieth century
was a highly persistent process, it is possible that
the observed persistence may result from the way
that monetary policy was implemented. Unlike
organized asset markets, where economic theories
suggest that price changes should approximate
a random walk, there is no strong theoretical

Each month’s release can be found at http://www.clevelandfed.org/research/data/mcpipr.htm.

3

MONETARY POLICY AND INFLATION

basis for highly persistent inflation rates. Recent
research suggests that the persistence of inflation
in the U.S. has diminished since the mid 1980s.2
Economic historians who study the gold standard
period conclude that inflation in various countries
was much less persistent during that period than
in the twentieth century. The lesson for those
trying to separate inflation signals from inflation
noise is that the filters may not be robust to
changes in monetary policy regimes.

FORECASTING INFLATION
A critical question for all central bankers, and
the FOMC in particular at the present time, is
how inflation will evolve in the near future. Are
near-term inflationary (or deflationary) pressures
really quiescent? The answer to this question
requires a forecasting model, or alternatively a
set of leading indicators of inflation.

Supply Chain Theories of Inflation
One view that currently is receiving considerable attention is what I will label the “supply
chain theory of inflation.” Proponents of this view
characterize inflation shocks as originating in
raw materials markets and subsequently transmitted through intermediate products to finished
products and finally to consumer prices. From
this perspective, inflation of commodity prices
is a leading indicator of PPI inflation which in
turn is a leading indicator of consumer price
inflation.
To proponents of the supply chain view, rapid
inflation in scrap steel prices and other basic
commodity prices in the past six months is a
cause of significant concern. Last month, a Wall
Street Journal article reported that some firms are
passing along materials price increases. “Indeed
a handful of companies—among them makers of
mattresses and gym equipment—already has or
are preparing to ask shoppers to pay more to cover

their rising steel costs. But most other manufacturers are trying to push steel-price jumps of up
to 30 percent to 50 percent to other companies
along the supply chain, creating tension between
steel producers, their biggest customers and
numerous smaller suppliers between them.”3
Similar concerns are often expressed about the
depreciation of the dollar against the currencies
of our major trading partners as a source of CPI
inflation directly through the price of imported
goods or indirectly through induced price changes
on domestically produced goods that compete
with imports.
Without question, individual firms often do
pass along increases in prices of their inputs.
The issue is whether this phenomenon is general
enough to explain overall inflation. Undoubtedly
there are times during which inflation shocks
are transmitted through such mechanisms. However such forces are not universal. Automobile
manufacturers, faced with weak demand in recent
years have effectively cut retail prices through
incentive programs, discounts, rebates and zero
interest financing. In this environment, they have
demanded and obtained substantial price concessions from their suppliers. In this case, downward
price pressures have been transmitted backward
through the supply chain starting from retail markets rather than forward from commodity markets.
Backward and forward price pressures can
exist at the same time. The forward pressures
have been visible recently in some industries,
but backward pressures have been evident for
several years and seem less newsworthy at present.
Competitive forces can frustrate efforts to push
increased input costs up the supply chain. The
Wall Street Journal, also in an article last month,
reported that airlines, facing substantial increases
in jet fuel prices “have made at least 12 attempts
to boost airfares in the past 2½ months alone.
But most of the efforts have failed to stick, and
increasingly the spoiler has been one or more

2

See T. Cogley and T. Sargent, “Evolving Post-World War II U.S. Inflation Dynamics,” NBER Macroeconomics Annual, 2001, pp. 331-72; and
A. Levin and J. Piger, “Is Inflation Persistence Intrinsic in Industrial Countries?” Federal Reserve Bank of St. Louis Working Paper 2002-023.

3

“Companies Fight Rising Steel Prices,” Wall Street Journal, March 8, 2003, p. A3

4

Inflation Signals and Inflation Noise

budget-price airlines, which see a chance in the
current squeeze to extend their market shares.”4
In this case competition in consumer markets is
limiting the transmission of price pressures
through the supply chain.
Nor are exchange rate depreciations necessarily leading indicators of price changes at the
retail level. First, the U.S. remains a relatively
closed economy with a large fraction of the goods
and services consumed here produced domestically. Second, research indicates that the “passthrough” of exchange rate fluctuations is not
instantaneous, complete or constant.5
There are several ways to test the idea that
inflation at an earlier stage of processing feeds into
inflation at a latter stage. Consider a statistical
equation in which we try to explain monthly CPI
inflation from the producer price index. The
consumer price index is an index of retail prices.
The PPI, which used to be called the “wholesale
price index,” is an index of prices at an earlier
stage of production. The equation employs two
groups of explanatory variables. The first group
consists of the previous 12 months of CPI inflation.
We include the CPI history because we want to
determine the contribution of the PPI over and
above the contribution of the CPI history itself.
The second group consists of the contemporaneous and previous 12 months inflation of the PPI
price index for finished goods.
Most of the predictive value is in the contemporaneous PPI term and the lagged CPI inflation
terms. The fact that the contemporaneous CPI
and PPI inflation rates move together is a consequence of inflation shocks that affect prices at all
stages of processing at the same time.6 The twelve
lagged PPI variables account for only 11 percent
of the variance in the CPI inflation not attributable to the contemporaneous PPI inflation and the

history of CPI inflation itself. Thus, we simply
do not observe PPI inflation being passed along
over time into the CPI to any significant degree.
Another approach to testing the supply-chain
theory of inflation is to examine the relationship
between various stages of processing in the PPI.
It turns out that the lead/lag relationship for the
PPI stage of processing is even weaker than that
for the PPI and CPI. Consider the statistical equation explaining PPI inflation for finished goods
using the history of finished goods inflation and
the current and previous 12 months inflation of
the PPI index for intermediate products. The intermediate products inflation adds less than 1 percent to the predictive value of the equation. Using
the same approach to explain the inflation rate
for the PPI for intermediate products, we find that
inflation in the PPI index for crude materials
adds only 4 percent to the predictive value of
the equation.
To summarize this discussion, although it may
seem logical that increases in crude materials
prices, such as petroleum, would feed forward
into semi finished goods and then forward again
to finished goods, in fact the inflation process
does not work this way. Depending on conditions
in individual markets, sometimes inflation does
feed forward, but sometimes it feeds back. We just
cannot reliably conclude that today’s materials
prices inflation will be tomorrow’s finished goods
inflation.

“Gap” Theories of Inflation
Another popular framework in which to
analyze the transmission of inflation is the “gap”
model. Various implementations of this model
are rooted in the expectations-augmented Phillips
curve. A typical empirical representation of this

4

“Growing Heft Puts Budget Airlines in the Pilot’s Seat,” Wall Street Journal, March 29, 2004, p. A1.

5

See P.K. Goldberg and M.M. Knetter, “Goods Prices and Exchange Rates: What Have We Learned?” Journal of Economic Literature, 1997,
35(3), pp. 1243-72; and P.S. Pollard and C.C. Coughlin, “Size Matters: Asymmetric Exchange Rate Pass-Through at the Industry Level,”
Federal Reserve Bank of St. Louis Working Paper 2003-029C.

6

The simple correlation between monthly percentage changes of the PPI crude materials price index and the PPI intermediate products price
index is 0.48; between percentage changes in the PPI intermediate products price index and the PPI finished products price index is 0.74
and between percentage changes in the PPI finished products price index and the CPI is 0.64 over the period March 1948 through December
2003.

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MONETARY POLICY AND INFLATION

framework postulates that the inflation rate is
determined by inflation expectations, current
and lagged values of a “gap measure,” current
and lagged “supply shocks” and undetermined
residual factors. In these equations, a common
specification of supply shocks includes changes
in the relative prices of food and energy, changes
in relative import prices, and “productivity
shocks.” “Gaps” typically are measured as the
difference between real GDP and a measure of
“potential GDP” such as that constructed by the
Congressional Budget Office, or by the deviation
of the unemployment rate from an estimated
equilibrium unemployment rate.7
There are several tricky parts of such analyses;
one is uncertainty over the level of potential GDP
or of the equilibrium unemployment rate. Another
is obtaining a reliable measure, or proxy, for the
expected rate of inflation. To measure expected
inflation, one of two approaches is frequently
applied. The first is to represent expected inflation
as a weighted average of past observed rates of
inflation. The alternative approach is to embed
the gap equation within a model of the entire economy and to equate expectations of future inflation
with the model based forecasts of inflation.8
Recent research at the Federal Reserve Bank
of St. Louis shows that with several different
models of expected inflation, including the lagged
inflation proxy, neither the “gap” term nor the
“supply shock” terms account for the major movements in the rate of inflation. The expected inflation term trumps the other factors as the major
moving force in the U.S. inflation history.

ing inflation.9 The focus of their analysis was
forecasts of inflation on a twelve-month horizon.
They started their analysis with “conventional
specifications of the Phillips curve” that related
the change in the inflation rate to past values of
an unemployment gap measure, past changes of
inflation and current and past values of various
measures of “supply shocks”—the type of specification discussed above.
Stock and Watson reached several
conclusions:

FORECASTING INFLATION—
EMPIRICAL EVIDENCE
In 1999, James Stock and Mark Watson published an exhaustive study of models for forecast-

1. In out-of-sample forecasts the various supply shock measures did not improve the
forecasting performance of their models;
2. while the estimated relationship between
changes in the inflation rate and current
and past changes in inflation and unemployment fail statistical tests for stability,
in economic terms the relationship is
robust;
3. alternative measures of real economic
activity generate more accurate forecasts
than do equations with the unemployment
rate;
4. the addition of interest rates and interest
rate spreads fails to improve the forecasting
performance of the estimated model;
5. commodity prices do not improve inflation
forecasts; and
6. forecasts using the unemployment rate outperform simple models using only lagged
changes in inflation, but the gain in forecasting accuracy is relatively small. Their
analysis is wide ranging covering a total of
168 economic indicators. An overall assessment of their results is that our ability to
deliver significantly more accurate forecasts
of inflation beyond those that can be generated from the history of inflation itself is
quite limited.

7

Robert J. Gordon has authored numerous studies applying this framework.

8

R. Clarida, J.; Gali and M. Gertler, “The Science of Monetary Policy: A New Keynesian Perspective,” Journal of Economic Literature,
December 1999, 37(4), pp. 1661-704.

9

J.H. Stock and M.W. Watson, “Forecasting Inflation,” Journal of Monetary Economics, 1999, 44, pp. 293-335.

6

Inflation Signals and Inflation Noise

ANCHORING INFLATION
EXPECTATIONS
How is a monetary policymaker to interpret
the above conclusions? One possible reaction
would be despair—it is close to impossible to
discern that near future inflation will differ systematically from recent past inflation and society
will just have to live, at least for a while, with
recent history.
I have an optimistic alternative interpretation
of the available data and research results. My
conclusion is that the unfolding inflationary
experience is most strongly anchored by how the
public and financial market participants expect
inflation to evolve. Well designed and articulated
policy under such conditions can produce great
outcomes. However, badly designed policies
under the same conditions can produce disasters!
If my characterization of the importance of
inflationary expectations as a determinant of
inflation is correct, then there are important lessons for monetary policymakers. In an economy
that works this way, it is essential that the central
bank clearly articulate its inflation objectives, and
have this message regarded as highly credible. If
a central bank is committed to a low-inflation
environment, and that commitment is credible,
then the general public will believe future inflation will be low. Under these circumstances the
economy has a strong external nominal anchor.
That nominal anchor generates behavior by buyers
and sellers that produces low and stable realized
inflation. In recent vernacular, at any given time
few firms in the economy have any “pricing
power.”
In this type of economy, if the central bank
fails to articulate an inflation objective, or if it
lacks credibility with the public that the stated
objective will be pursued, then the downside risk
to the economy is enormous. Environments in
which expectations are not anchored externally
are inherently unstable. We observe this behavior
10

in asset markets when, for reasons that are not
well understood, “bubbles” develop. Reality
chases expectations, which in turn chase reality.
Events are determined by “inflationary psychologies.” Prices follow explosive paths, either upward
or downward, for a time.
Within a few weeks of the dramatic change
in policy direction in 1979, Chairman Volcker
testified before Congress on the FOMC’s new
operating procedures. Market expectations played
a prominent role in his thinking. “The clear and
present danger was that failure to deal with inflation and inflationary expectations would in time
produce more—not less—economic instability,
ultimately with higher prices and greater unemployment. In that setting, the priority for policy
was decisive action to deal with inflationary
pressures and to defuse the dangerous expectational forces that were jeopardizing the orderly
function of financial and commodity markets.”10

CONCLUDING COMMENT
The FOMC is unavoidably in a situation of
having to apply its best judgment to a variety of
economic indicators of possible inflationary pressure. I’ve not discussed today a range of information on inflation pressures, which include the
rate of productivity growth, the rate of increase
in unit labor costs, measures of wage inflation
anecdotal reports from business firms on the inflation environment they see. Instead, I hope I’ve
convinced you that there is no regular and reliable relationship between inflation in materials
prices or goods at an early stage of processing
and retail price inflation.
Of critical importance to maintaining low
and stable inflation is the FOMC’s commitment
to act aggressively when inflation risks change,
either up or down. That commitment anchors
market expectations of long-run inflation, and
makes the economy more robust to short-run
inflation shocks. Short-run disturbances do not

Statement by Paul A. Volcker before the Subcommittees on Domestic Monetary Policy and on International Trade, Investment and Monetary
Policy of the Committee on Banking, Finance and Urban Affairs, U.S. House of Representatives, Nov. 13, 1979, Federal Reserve Bulletin,
December, 1979, p. 959.

7

MONETARY POLICY AND INFLATION

automatically get built into inflation, which helps
to dampen the impacts on the economy of inflation shocks.
This stable environment also helps the FOMC
to avoid mistakes. Above all, we do not want to
respond to inflation noise, which would add further instability to the economy. Extracting the
inflation signal, and responding to it, is what we
try to do.

8