Causality links between consumer and producer prices: Some empirical evidence.
Pittis, Nikitas
Guglielmo Maria Caporale (*)
Margarita Katsimi (+)
Nikitas Pittis (++)
This paper reexamines the relationship between consumer and
producer prices in the G7 countries (United States, Canada, Germany,
France, Italy, United Kingdom, and Japan), and it improves on the
existing literature in two ways. First, it takes into account causality links arising from the transmission mechanism of monetary policy, which
are generally overlooked. Second, it employs the causality testing
method for unstable systems recently introduced by Toda and Yamamato
(1995), which results in standard asymptotics, thereby obtaining valid
statistical inference. The empirical results are consistent with the
conventional wisdom according to which there is unidirectional causality
running from producer to consumer prices, bidirectional causality (or
even no significant links) only being found when the causality links
reflecting the monetary transmission mechanism are ignored.
1. Introduction
The relationship between consumer and producer prices has often
been characterized in the literature as a one-sided lag structure, with
producer prices leading. This is reported, for instance, by Silver and
Wallace (1980), who carried out Sims causality tests and also used the
Hatanaka and Wallace (1979) procedure to estimate the parameters of the
lag distribution (see also Engle 1978; Guthrie 1981). Colclough and
Lange (1982), though, took issue with these authors, noticing that there
are theoretical reasons to expect causality to run also from consumer
prices to producer prices. Furthermore, in the earlier study, the Sims
test had not been applied adequately, that is, the significance of the
leads as a group had not been tested. Instead, Colclough and Lange
(1982) performed both Granger and Sims tests and concluded that in fact
causality runs in the opposite direction or might be bidirectional. In
both cases, only U.S. data were used.
Additional evidence was provided by Cushing and McGarvey (1990,
hereafter C&M), who concluded that "the magnitude of feedback
from producer to consumer prices is greater than that from consumer to
producer prices," to the extent that a one-sided Granger causal
pattern can be assumed, as consumer prices have very little incremental
power. They also argued that the addition of the money supply does not
produce significant changes, the feedback from producer to consumer
prices still dominating, and that such a causal ordering is perfectly
consistent with a flexible price model with strong demand effects.
Robust evidence on the causality links between producer and
consumer prices is of crucial importance, as, unless there are only
unidirectional links from producer to consumer prices, the producer
price index, which is often used as a leading indicator for inflation,
might not in fact be very informative about future inflation. (1)
Therefore, this paper reexamines the relationship between consumer and
producer prices in the G7 countries and differs from earlier
contributions, in particular, the study by C&M, in three important
respects. First, our analysis avoids an important possible source of
bias affecting other studies on this topic, that is, the omission of
monetary variables (this is in contrast to the theoretical setup of
C&M, which implies unidirectional causality from wholesale to
consumer prices). As shown in Caporale and Pittis (1997), leaving out
"relevant" variables can invalidate causality inference. We
show that, contrary to what C&M argue, including variables that
capture the monetary transmiss ion mechanism affects inference
dramatically, unidirectional causality being found where previously
causality appeared to run often in both directions--causality from
producer to consumer prices is found in all cases. Second, we adopt an
appropriate methodology for carrying Out causality tests within systems
that might be unstable. This is the causality testing strategy recently
introduced by Toda and Yamamoto (1995), which results in standard
asymptotics and valid inference. Compared to other approaches, such as
the one advocated by Toda and Phillips (1993), it also has the advantage
that it does not require any pretesting in order to determine the
dimension of the cointegration space, and it is relatively easy to
implement in practice. Third, we provide evidence for the G7 countries
as opposed to the United States only.
The layout of this paper is as follows. Section 2 provides a brief
overview of the theoretical arguments on the relationship between
consumer and producer prices. Section 3 discusses the consequences of
adopting an "incomplete" model for causality inference and
suggests an appropriate testing strategy for the case of unstable
systems. Section 4 presents the empirical results. Section 5 offers some
concluding remarks.
2. An Economic Interpretation of the Relationship between Consumer
and Producer Prices
The producer price index (PPI) is widely used as a leading
indicator for the consumer price index (CPI). This causality is related
to supply-side developments and stems mainly from the production timing:
The retail sector adds value with a lag to existing production. In the
framework of a fairly standard open economy macro model, (2) the retail
sector uses existing domestic production as an input. Consumer prices
will depend on the producer price of the home good, the price of the
imported good, the exchange rate, the level of indirect taxes, the
marginal cost of retail production, and a possible markup. A fully
fledged model that offers a theoretical basis for Granger causality from
wholesale to consumer prices is the one developed by Gushing and
McGarvey (1990). In their model, the production of final goods in each
period uses primary goods produced in the previous period as input, so
that supply-side disturbances in the primary goods market affect
wholesale prices and consumer prices in the next period. Th ey find
that, as long as primary goods are used with a lag as input in the
production of consumption, wholesale prices will Granger cause consumer
prices independently from the parameters governing the exogenous stochastic processes.
In a subsequent paper, Colclough and Lange (1982) argued that the
causality from consumer prices to producer prices had not received much
attention in the literature. Their theoretical argument stems from
derived demand analysis. (3) The demand for final goods and services determines the demand for inputs between competing uses. In this
framework, the cost of production reflects the opportunity cost of
resources and intermediate materials, which in turn reflects the demand
for final goods and services. The obvious implication is that consumer
prices should affect producer prices. The theoretical model of Gushing
and McGarvey (1990) investigates this link by allowing for demand-side
effects: Demand for primary goods depends on the expected future price
of consumer goods. Under this assumption, the consumer price will depend
on current demand and past expectations of current demand, whereas the
wholesale price depends on expected future demand. A Granger causal
relationship running from consumer to wholesale pr ices would exist only
for certain values of the disturbances' parameters.
Consumer prices may also affect producer prices through labor
supply if wage earners in the wholesale sector aim at preserving the
purchasing power of their income. Whether this effect occurs with a lag
or instantaneously will probably depend on the nature of the
wage-setting process and the expectations formation mechanism. (45) In
addition, whether an increase in consumer prices can feed through to
producer prices will depend critically on the behavior of monetary
authorities. If the monetary authority announces an inflation target,
which is considered to be credible by wage setters, then an increase in
consumer price inflation above the central banks' target rate is
perceived as temporary and has no effect on wages and, hence, producer
prices. (6)
3. Econometric Issues
Two econometric issues that arise when testing for links between
consumer and producer prices are selecting the "correct" model
in the context of which causality relationships are to be analyzed and
carrying out tests that result in valid statistical inference.
The first issue is addressed by Caporale and Pittis (1997), who
analyze how causality inference in the context of a bivariate vector
autoregression (VAR) is affected by the omission of a third relevant
variable and show that in general this results in invalid inference
about the causality structure of the bivariate system (see also
Lutkepohl 1982). More specifically, they examine how causality inference
within a system consisting of [y.sub.t] and [x.sub.t] is affected by the
omission of another variable, [w.sub.t], which causes (i) none, (ii)
one, and (iii) both the variables in the VAR. They also derive
conditions under which causality inference is invariant to the selection
of a bivariate or a trivariate model. The most general condition for
invariance to model selection requires the omitted variable not to cause
any of the variables in the bivariate system, although it allows the
omitted variable to be caused by the other two. (7)
As for causality testing in unstable, possibly cointegrated VARs,
(8) this issue was initially analyzed by Sims, Stock, and Watson (1990)
in the context of a trivariate VAR and then examined in a more general
setting by Toda and Phillips (1993). These studies show that, in
general, Wald test statistics for noncausality restrictions in the
context of the unrestricted VAR will have nonstandard limit
distributions in which nuisance parameters are also present, although
they will have a [chi square] asymptotic distribution, free of nuisance
parameters, if there is "sufficient" cointegration with
respect to the variables whose causal effects are being tested (see Toda
and Phillips 1993, 1994). This depends on the presence and location of
unit roots in the VAR. Unfortunately, this information is difficult to
obtain from the estimation of a VAR in levels. In particular, sequential
testing strategies, such as the one developed by Toda and Phillips
(1993), where the cointegration rank has to be determined before carry
ing out causality tests, are potentially subject to severe pretesting
biases, as the tests for cointegration ranks in Johansen-type error
correction models (ECMs) are very sensitive to the values of the
nuisance parameters (see Toda 1995). Therefore, it would be useful to be
able to rely on an alternative testing procedure that does not require
pretesting for the cointegration properties of the system. Such a
procedure has recently been developed by Toda and Yamamoto (1995) and is
summarized in the following.
The basic idea is to artificially augment the correct order, say,
k, of the VAR by the maximal order of integration, say, [d.sub.max],
exhibited by the process of interest. One can then estimate a (k +
[d.sub.max]) th-order VAR and ignore the coefficients of the last
[d.sub.max] lagged vectors and test linear or nonlinear restrictions on
the first k coefficient matrices by means of a Wald test, using the
standard asymptotic theory.
To be more specific, consider the following VAR, which allows for a
linear trend:
[Z.sub.t] = [PHI] + [PHI]t + [[PI].sub.1][Z.sub.t-1] + ... +
[[PI].sub.k][Z.sub.t-k] + [E.sub.t], t = 1, ..., T (1)
where [E.sub.t] ~ N(0, [OMEGA]).
Suppose that we are interested not in the integration/cointegration
properties of Equation 1 but rather in testing economic hypotheses that
can be expressed as restrictions on the coefficients of the model as
follows:
[H.sub.0]:f([pi]) = 0, (2)
where [pi] = vec(P) is a vector of parameters from the model (Eqn.
1), P = [[PI].sub.1], ..., [[PI].sub.k]], and f(.) is a twice
continuously differentiable m-vector valued function with F([phi]) =
[phi]f([phi])/[phi][phi]' and rank (F(.)) = m.
Assume that the maximum order of integration that is expected to
characterize the process of interest is at most two, that is,
[d.sub.max] = 2. Then, in order to test the hypothesis (Eqn. 2), one
estimates the following VAR by ordinary least squares (OLS):
[Z.sub.t] = [[PHI].sub.0] + [[PHI].sub.1]t +
[[PI].sub.1][Z.sub.t-1] + ... + [[PI].sub.k][Z.sub.t-k] +
[[PI].sub.k+1][Z.sub.t-k-1] ... + [[PI].sub.p][Z.sub.t-p] + [E.sub.t]
(3)
where p [greater than or equal to] k + d = k + 2, that is, at least
two more lags than the true lag length k are included. The parameter
restriction (Eqn. 2) does not involve the additional matrices
[[PI].sub.k+1],..., [[PI].sub.p], since these consist of zeroes under
the assumption that the true lag length is k.
Equation 3 can be written in more compact notation as follows:
[Z.sub.t] = [PHI][[tau].sub.t] + P[x.sub.t] + [psi][y.sub.t] +
[E.sub.t], (4)
where
[PHI] = [[[PHI].sub.0], [[PHI].sub.1]], [[tau].sub.t] = [1, t],
[x.sub.t] = [[Z'.sub.t-1],..., [Z'.sub.t-k]]', [y.sub.t]
= [[Z'.sub.t-k-1],..., [Z'.sub.t-p]]',
P = [[[PI].sub.k+1],..., [[PI].sub.k]], [psi] =
[[[PI].sub.k+1],..., [[PI].sub.p]],
or, in the usual matrix notation,
Z' = [PHI]T' + PX' + [psi]Y' + E', (4a)
where X = [x.sub.1],..., [x.sup.T]' and so on.
One can then construct the following Wald statistic [W.sub.2], to
test the hypothesis (Eqn. 2):
[W.sub.2] = f([PHI])'[[F([PHI]){[[SIGMA].sub.E] [cross
product] [(X'QX).sup.-1]}F([PHI])'].sup.-1]f([PHI]) (5)
where [[SIGMA].sub.E] = [T.sup.-1]E'E, Q = [Q.sub.[tau]] -
[Q.sub.[tau]][(Y'[Q.sub.[tau]]Y).sup-1] Y&prime[Q.sub.[tau]],
and [Q.sub.[tau]] = [I.sub.T] - T[(T'T).sup.-1]T'.
Toda and Yamamoto's theorem 1 (1995, pp. 234-5) proves that
the Wald statistic (Eqn. 5) converges in distribution to a [chi square]
random variable with m degrees of freedom, regardless of whether the
process [Z.sub.t], is stationary, I(1), I(2), possibly around a linear
trend, or whether it is cointegrated.
Since the true lag length of the process is rarely known in
practice, this method also requires some pretesting to determine it.
Sims, Stock, and Watson (1990) were the first to show that lag selection
procedures, commonly employed for stationary VARs, which are based on
testing the significance of lagged vectors by means of Wald (or LM or
LR) tests, are also valid for VARs with I(1) processes, which might
exhibit cointegration. Toda and Yamamoto (1995) proved that the validity
of this argument can be extended to processes with an order of
integration higher than one, as long as the true lag length is greater
than or equal to the order of integration. In other words, the
asymptotic distribution of a Wald or likelihood ratio test for the
hypothesis that the lagged vector of order p is equal to zero is [chi
square], unless the process is Markovian and I(2).
4. Empirical Results
The empirical analysis was carried out for the G7 countries. We
estimated first a bivariate VAR consisting of the logarithms of consumer
price and producer price indices in addition to a constant and a linear
time trend. The series are quarterly and were obtained from Datastream.
The corresponding national data sources are the following: Bank of
Canada, Banque de France, Deutsche Bundesbank, Istituto Nazionale di
Statistica, Bank of Japan, Bank of England, and Federal Reserve. The
selected sample goes from 1976:1 to 1999:4. A VAR including earlier
observations was found to exhibit parameter instability, which would
result in invalid statistical inference. The observed instability was
not purely of the type that could be handled by the inclusion of impulse
dummies but appeared to reflect regime changes. This is not surprising,
as in the period before the first quarter of 1976, two major structural
breaks occurred, namely, the first oil shock and the transition from
fixed to flexible exchange rates, the latter of which generated more
persistent inflation (see Alogoskoufis and Smith 1991).
As suggested by Toda and Yamamoto (1995), the first step consists
of determining the order of the VAR, so as to artificially augment it at
a later stage by the maximum order of integration of the series
involved. We started by estimating a VAR(5) and then dropped one lag at
a time. Their significance was tested by means of F-statistics, which,
as already mentioned, have standard limit distributions and therefore
result in valid inference on the order of the VAR. The SIC for the
optimal order selection was also used as a further check on the optimal
lag length. Moreover, misspecification tests were carried out for serial
correlation and/or dynamic heteroskedasticity in the residuals of the
VAR, since the Toda and Yamamoto procedure assumes i.i.d. errors. The
results (not reported) suggest that the optimal lag length for the
bivariate VAR is 2 for the United States, Italy, Germany, France, and
Canada and 3 for Japan and the United Kingdom.
The next step is to estimate VARs artificially augmented by the
maximum order of integration in the series. It is quite natural to
assume that the logs of CPI and PPI are at maximum I(2), since there is
some evidence that inflation series might be I(1). Therefore, we
augmented the bivariate VARs estimated previously by two lags and tested
for noncausality zero restrictions on the parameters of the original
VARs. The results are presented in Table 1. In the case of Canada, there
is no causality at all; in the case of France and Germany, there is
causality in one direction, running from PPI to CPI; and in the rest of
the cases, namely, Italy, Japan, the United Kingdom, and the United
States, the evidence points toward bidirectional causality. This
evidence is not consistent with the conventional wisdom according to
which producer prices lead consumer prices.
As argued previously, the omission of an important causing variable
from the bivariate system may significantly affect inference on
causality between the variables in the bivariate system. We therefore
considered a five-variate VAR, including the money supply (M1), real
gross domestic product (GDP), and the three-month interest (the data
sources being the same as before). (9) The inclusion of these variables
aims at capturing the transmission mechanism of monetary policy. (10) As
in the bivariate case, we first tested for the order of the VARs. The
results from the selection procedure, together with the misspecification
tests, suggest that the order of the VARs in the five-variate case are
as follows: US = 3, UK 2, JP 3, IT = 2, GE = 3, FR = 2, and CA = 4. As
previously, we augmented the five-variate VARs by two additional lags,
since the maximum order of integration of the additional variables is
not expected to be greater than two.
The results are reported in Table 2 and can be summarized as
follows. In the case of Canada, for which there was no evidence of any
causality links between CPI and PPI in the bivariate model,
unidirectional causality running from PPI to CPI is now found. This is
consistent with the theoretical results discussed previously, according
to which the omission of a relevant causing variable is likely to affect
inference on causality between the original two. In the present context,
causality appears to be running from M1 to CPI. Some evidence for
causality running from M1 to PPI is also detected. As a consequence, the
bivariate findings on causality links between CPI and PPI are reversed.
In the case of Italy, M1 was found to cause PPI, and the interest rate
was found to cause PPI. The causality structure between CPI and PPI has
changed in the sense that now only unidirectional causality running from
PPI to CPI is detected. As for the United States, the interest rate was
found to cause CPI, which again resulted in detecting causality running
only from PPI to CPI. In the cases of France, Germany, and Japan, the
evidence also suggests that causality is unidirectional, running from
PPI to CPI. For the first two countries, the evidence is consistent with
that obtained from the bivariate analysis, although in the case of
France the "omitted" M1 seems to cause CPI and PPI. This is an
interesting case in which the omission of a variable does not alter
causality inference in the incomplete model, although it does affect the
estimates of the transition matrices corresponding to CPI and PPI, which
are different in the five-variate and bivariate case. Finally, in the
case of the United Kingdom, where the interest rate affects both CPI and
PPI, the causality inference drawn from the bivariate and the
five-variate models is different. In the five-variate model, we detect
unidirectional causality running from PPI to CPI as opposed to the
bidirectional causality found in the bivariate model.
Table 2 provides strong support for unidirectional causality from
PPI to CPI for all countries. This unambiguous result is obtained by
taking into account two possibilities: the possibility that the VAR
contains unit roots of unknown number and location and that the VAR may
be incomplete. When these two factors are taken into account, the
results are clear and consistent with the predominant view that PPI is a
leading indicator for CPI. Although there are theoretical reasons to
expect causality to run also from CPI to PPI, this causality pattern is
not supported by the five-variate model. The causality from CPI to PPI
could be rationalized in a derived demand analysis framework where
demand for final goods affects the production cost through the price of
inputs. Moreover, causality from CPI to PPI may reflect the fact that
wage setters in the wholesale sector increase wages when they observe an
increase in consumer prices. The absence of this causality link when one
allows for the transmission of monetary pol icy may imply that monetary
authorities react to inflationary pressures so that the CPI impact on
PPI is eliminated through the inclusion of monetary variables.
5. Conclusions
This paper has provided some new evidence on the empirical
relationship between consumer and producer prices. In addition to having
a much wider country coverage, it has employed a causality testing
method that is appropriate even for systems that exhibit unit roots,
namely, the Toda and Yamamoto (1995) procedure, and it has addressed the
issue of the possible omission of relevant variables, such as the money
supply, interest rates, and output from the analysis. Valid statistical
inference has therefore been obtained. By contrast, existing empirical
studies are vitiated by their use of unreliable statistical tests and by
the adoption of "incomplete" models, where ignoring causality
links with other variables biases the results (see Caporale and Pittis
1997).
The empirical evidence is consistent with the conventional wisdom
according to which producer prices lead consumer prices. In all
countries, the causality structure confirms with the widely held prior
of a one-sided lag structure from producer to consumer prices.
Furthermore, it appears that the omission of variables capturing the
monetary transmission often results in misleading inference. Such
results significantly improve the findings of earlier papers, such as
the one by C&M, where a one-sided Granger causal structure was
preferred both on theoretical grounds (its consistency with flexible
price models with strong demand effects) and on empirical grounds (the
inclusion of money not being found to affect the inference), but where
causality testing was not based on valid asymptotics.
(*.) Centre for Monetary and Financial Economics, South Bank
University London, 103 Borough Road, London SEl OAA, UK; E-mail
[email protected]; corresponding author.
(+.) Department of International and European Economic Studies,
Athens University of Economics and Business, 76 Patision Avenue, 10434
Athens, Greece.
(++.) Department of Financial Management and Banking, University of
Piraeus, Karaoli--Dimitriou 80, 18534 Piraeus, Greece.
We are grateful to Stephen Hall and two anonymous referees for
useful comments and suggestions. The usual disclaimer applies.
Received February 2000; accepted March 2001.
(1.) Clark (1995) argues on theoretical grounds that the
pass-through effect from PPI to CPI may be weak. Using standard
causality tests, he finds some evidence that producer prices lead
consumer prices; by contrast, PPI changes appear not to be able to
predict systematically CPI changes. His inference, though, also has the
pitfalls discussed here.
(2.) For example, see Alogoskoufis and Martin (1991).
(3.) Derived demand analysis was first developed by Marshall
(1961).
(4.) Wages in the wholesale sector may be determined a period in
advance so that they will depend on past expectations of current
inflation, or they may be determined in each period according to current
consumer price inflation. Moreover, wage agreements may include catch-up
clauses that relate wages' growth to past inflation.
(5.) Even if consumer prices affect cost and prices in the
wholesale sector with a lag, the presence of Granger causality cannot be
inferred without examining the properties of the stochastic disturbances.
(6.) This argument has first been demonstrated by Barro and Gordon
(1983).
(7.) A complete analysis of causality and forecasting in incomplete
systems can be found in Caporale and Pittis (1997).
(8.) For more details, see Caporale and Pittis (1999).
(9.) These variables are also included in VAR models aiming at
investigating the real effects of monetary aggregates, such as Clarida
and Gali (1994) and Coebrane (1998).
(10.) For an extended discussion on the transmission mechanism,
see, among others, Duguay (1994).
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Table 1
Bivariate VAR
Wald Tests Based on
Artificially Augmented, d = 2
(p-values)
Null
Hypothesis CA FR
PPI does not cause CPI 0.069 0.001
CPI does not cause PPI 0.136 0.375
Wald Tests Based on
Artificially Augmented, d = 2
(p-values)
Null
Hypothesis GE IT JP UK US
PPI does not cause CPI 0.016 0.046 0.000 0.000 0.934
CPI does not cause PPI 0.352 0.000 0.039 0.007 0.002
The results suggest that the optimal lag length is 2 for the United
States, Italy, Germany, Frances, Canada and 3 for Japan and the United
Kingdom.
Table 2
Five-Variate VAR
Wald Tests Based on Artifically
Augmented VAR9k), d = 2
(p-values)
Null
Hypothesis CA FR
PPI does not cause CPI 0.021 0.002
CPI does not cause PPI 0.344 0.613
M does not cause CPI 0.003 0.006
M does not cause PPI 0.077 0.003
Y does not cause CPI 0.171 0.302
Y does not cause PPI 0.920 0.994
R does not cause CPI 0.467 0.223
R does not cause PPI 0.142 0.640
Wald Tests Based on Artifically
Augmented VAR9k), d = 2
(p-values)
Null
Hypothesis GE IT JP UK US
PPI does not cause CPI 0.000 0.040 0.000 0.000 0.055
CPI does not cause PPI 0.341 0.101 0.136 0.119 0.059
M does not cause CPI 0.891 0.336 0.005 0.868 0.563
M does not cause PPI 0.904 0.008 0.530 0.316 0.873
Y does not cause CPI 0.430 0.688 0.712 0.119 0.695
Y does not cause PPI 0.211 0.091 0.309 0.686 0.484
R does not cause CPI 0.158 0.040 0.274 0.005 0.002
R does not cause PPI 0.296 0.118 0.226 0.019 0.572
M, Y, and R stand for money supply (Ml), real GDP, and three-month
interest rate, respectively. The order of the VARs are as follows: US =
3, UK = 2, JP = 3, IT = 2 GE = 2, GE = 3, FR = 2, CA = 4.