Exchange Rate Shocks and the Speed of Trade Price Adjustment.
Balvers, Ronald
Jimmy Ran [+]
Ronald Balvers [*]
A quantity adjustment cost model is developed in the context of
international trade along the lines proposed by Krugman (1987). The
model implies that prices adjust dynamically to exchange rate
fluctuations. The price adjustment speed is determined as a function of
foreign demand responsiveness, the appropriate discount rate, and an
adjustment cost parameter. Passthrough is incomplete and increases over
time and with the speed of price adjustment. A preliminary empirical
analysis finds that the speed of price adjustment from the time series
by industry and then in a cross-sectional regression tentatively relates
the obtained adjustment speeds to their theoretical determinants.
1. Introduction
Theoretical and empirical work in the international trade
literature dealing with the relationship between exchange rate and trade
prices has been dominated and guided by the static pass-through and
profit markup model [1] (see, e.g., Feinberg 1986; Mann 1986; Fisher
1989; Hooper and Mann 1989; Knetter 1989; Gagnon and Knetter 1995;
Feenstra, Gagnon, and Knetter 1996; and Lee 1997). The shortcoming of
such models is well captured by William Branson (1989, p. 333):
Difference in adjustment response signals to me the need for a
reconsideration of the theoretical framework for the analysis of the
pass-through question. By now, we should be thinking about optimizing
price policy for investors and exporters who know that they face an
exchange rate that follows some sort of stochastic process over time.
These differences call for a revision of pass-through theory along the
lines of time series analysis.
Our explicit incorporation of profit-maximizing firms facing
adjustment costs develops the model introduced by Krugman (1987). It
transforms the traditional markup and pass-through model to explain from
first principles a dynamic markup and a price adjustment speed, both
depending on fundamental characteristics of the firms involved. Krugman
(1989) concludes his paper on pricing to market by calling for further
research on the adjustment cost model. Regarding the adjustment cost
approach, he states (Krugman 1989, p. 44),
It is still a speculative idea, not grounded in solid empirical
tests; but it is a good story, and if it is correct, it has extremely
important implications for economic policy.
The present paper provides the quantity adjustment cost approach
that Krugman calls for. As such, it complements the work of Gagnon
(1989) and Kasa (1992). While Gagnon and Kasa employ quantity adjustment
cost models with many of the same features as the model developed here,
they provide only approximate solutions and focus on a quite different
set of issues. Gagnon examines the effect of exchange rate variability
on trade volume. Kasa investigates the importance of mean reversion in
exchange rates as an explanation for the pricing to market hypothesis.
In contrast, our focus is on the relation between adjustment speeds and
pass-through. Thus, our contribution relative to Gagnon (1989) and Kasa
(1992) is that we provide the passthrough issue in a dynamic context
with exact analytical solutions that relate the degree of passthrough to
adjustment speeds and identify the determinants of commodity-specific
adjustment speeds in response to exchange rate shocks.
The remainder of the paper is organized as follows. In section 2 we
develop a partial equilibrium model, taking exchange rates as given, of
the pricing policies of a profit-maximizing firm competing in foreign
markets and subject to a convex quantity adjustment cost. Section 3
develops testable implications directly from the model. Section 4
discusses the data and empirical methodology for preliminary two-stage
time-series and cross-sectional tests. Section 5 provides the tentative
estimation, and section 6 concludes.
2. A Simple Partial Equilibrium Model
Consider a representative firm producing for export that maximizes
the expected discounted value of infinite horizon real profits. The firm
generates its revenue abroad in foreign currency. It has no influence on
the exchange rate, may adjust its price at any point in time, but is
subject to a convex cost of quantity adjustment. The firm maximizes
[pi] = E [[[integral of].sup.[infty]].sub.0] [e.sup.-rt][xpq -
c([w.sub.D], x[w.sub.F])q - [frac{1}{2}]xh[(q').sup.2]]dt, (1)
where x is the exogenously given real exchange rate at time t. We
define x as the units of domestic currency per unit of foreign currency
multiplied by the export destination country's price index and
divided by the home country's price index. Instantaneous profits
are discounted at a rate r, which is specific to the firm; this rate
accounts for a standard risk premium inherent in the riskiness of the
firm's activities. Price p is the real foreign currency-denominated
sales price in the foreign market at time t. Quantity q represents the
firm's export delivery at time t. The first term inside the
integral is the revenue obtained in the foreign country converted back
into home currency by the exchange rate. The second term is the
firm's (indirect) cost function. For simplicity, we assume that
production exhibits constant returns to scale in domestic inputs with
exogenous price [w.sub.D] and foreign inputs with exogenous foreign
price [w.sub.F] (which becomes x[w.sub.F] in home currency terms). We
thus consider a constant (i.e., independent of the production level)
marginal production cost c (which may include a transportation cost) as
a function of these input prices.
The last term in Equation 1 represents the convex quantity
adjustment cost (with parameter h), which is here assumed quadratic for
simplicity. In our continuous-time formulation, the change in quantity
is indicated conventionally by q'. Note that the adjustment cost is
viewed as incurred abroad so that its cost must be premultiplied by the
real exchange rate to convert back to domestic currency units. A
motivation for this adjustment cost formulation is provided by Krugman
(1987, p. 63): Temporary bottlenecks occur because of changing trade
volume. Sales cannot be expanded without an expansion of the
"infrastructure" related to sales, distribution, and service.
Thus, while production costs occur domestically, the quantity adjustment
costs may be viewed as occurring abroad and should be adjusted for real
exchange rate fluctuations.
For purposes of tractability, we consider a linear form for the
foreign demand curve
q = a - bp, (2)
where a and b are positive and finite-valued constants. The
finiteness of b reflects the assumption of price-setting power on the
part of the firms. The firm is assumed to compete monopolistically only
with foreign firms producing for their own market. [2] Strategic
interactions are ignored, not only for tractability but also because it
is difficult to choose one particular strategic game to be relevant for
the whole spectrum of industries we consider. As noted by Dornbusch
(1987), who employs a similar linear demand curve, all nonprice
determinants of demand are captured by the constant.
The decision problem for the exporting firm thus is to choose the
pricing process to maximize Equation 1 subject to Equation 2. The
model's functional form assumptions here are quite similar to the
assumptions in the models used in the related literature by Krugman
(1987), Gagnon (1989), and Kasa (1992), in particular, the partial
equilibrium formulation, the constant marginal production cost, the
monopolistic market form, the quadratic adjustment cost, and a specific
functional form for the demand curve. A dynamic programming approach
(derivation in the Appendix) produces the following solution:
[[p.sup.*].sub.t] = [[p.sub.0] -
[hat{p}]][e.sup.-[lambda][c.sup.t]] + [hat{p}] (3)
The optimal price at time t is a weighted average of the initial
price at time 0 and a steady-state equilibrium price [hat{p}], where the
weight on the initial price decreases with a negative exponential over
time at a rate, depending on the speed of price adjustment
[[lambda].sub.c]:
[[lambda].sub.c] = [frac{1}{2}] [[([r.sup.2] +
[frac{8}{bh}]).sup.1/2] - r][greater than] 0. (4)
The steady-state price is given by
[hat{p}] = [frac{ax + c([w.sub.D],x[w.sub.F])b}{2bx}]. (5)
3. Testable Implications of the Adjustment Cost Hypothesis
Taking the time derivative in Equation 3 produces [p'.sub.t] =
-[[lambda].sub.c][[p.sub.t] - [hat{p}]][e.sup.-[lambda][c.sup.t]].
Substituting into Equation 3 then yields
[p'.sub.t] = [[lambda].sub.c][[hat{p}] - [p.sub.t]]. (6)
Converting into discrete time for empirical purposes, we obtain
[p.sub.t] - [p.sub.t-1] = [lambda] ([hat{p}] - [p.sub.t-1]). (7)
Alternatively, a similar equation can be derived by setting t = 1
in Equation 3, so that the discrete-time approximation in Equation 7 is
exact if
[lambda] = 1 - [e.sup.-[[lambda].sub.c]] (8)
Equation 7 is the well-known partial price adjustment equation.
However, we have an endogenous description of the speed of price
adjustment [lambda] in Equation 4 and of the steady-state equilibrium
price [hat{p}] in Equation 5. Substituting [hat{p}] into 7, we obtain
[p.sub.t] = [alpha] + [beta][p.sub.t-1] + [gamma]C([w.sub.D]/x,
[w.sub.F]), (9)
where
[alpha] = [lambda][lgroup][frac{a}{2b}][rgroup], [beta] = (1 -
[lambda]), [gamma]=[frac{[lambda]}{2}], (10)
with 0 [less than] [lambda] [less than] 1 (or 0 [less than]
[[lambda].sub.c] [less than] [infty]). Equation 9 implies that the
inverse of the real exchange rate (or the domestic to foreign currency
real exchange rate) positively affects the export price as long as there
are any domestic inputs used in the production process. This follows
from the fact that the indirect cost function is increasing and
homogeneous of degree one in input prices so that c([w.sub.D],
x[w.sub.F])/x = c([w.sub.D]/x, [w.sub.F]).
Five testable implications follow directly from the previous
equations:
(i) [beta] [less than] 0: The speed of price adjustment is smaller
than one; that is, prices adjust slowly to shocks (Eqns. 9 and 10). This
requires of course that the adjustment cost, parameter h in Equation 4
be strictly positive.
(ii) [gamma][partial]c([w.sub.D]/x, [w.sub.F])/[partial](1/x)
[greater than] 0: The inverse real exchange rate positively affects the
export price denominated in the foreign currency (Eqns. 9 and 10). The
reason here is that a depreciation in real terms of the foreign currency
has a less than proportional impact on production costs, as long as any
domestic inputs are used, but for a given foreign-currency export price
proportionately raises the revenue from export in domestic currency
terms.
(iii) [beta] and [gamma][partial]c([w.sub.D]/X,
[w.sub.F])/[partial](1/x) are inversely related: Both depend on
[lambda]--[beta] inversely and [gamma] directly (Eqns. 9 and 10). The
reason is that slower adjustment in general also implies that the
initial effect of an exchange rate change is less pronounced.
Further testable implications can be obtained for estimated
[lambda]: Once speeds of price adjustment have been obtained, they can
be compared cross sectionally. Equation 4 together with Equation 8
implies the following:
(iv) [partial][lambda]/[partial]r [less than] 0: A higher rate of
discounting the future implies that the firm values the benefits of
quick price adjustment less, as the future opportunity cost of
deviations in price from the myopic optimum are weighted less heavily.
(v) [partial][lambda]/[partial]b [less than] 0: A more horizontal
demand curve causes the firm to adjust price more slowly. The reason is
that, for any given difference between the current and the steady-state
quantity, the difference between the current price and the steady-state
price is less. Thus, the cost of slow adjustment in terms of revenue
forgone is lower compared to the quantity adjustment cost.
Additionally, higher adjustment costs h decrease the optimal speed
of quantity adjustment, which in turn requires a lower speed of price
adjustment. This implication cannot be tested, however, since no proxies
for h are available.
The testable implications from our dynamic model should extend as
well as complement those that are explicit or implicit in the
predominantly static pass-through literature. [3] In this view, changes
in the nominal exchange rate (highly correlated with real exchange rate
changes) will be partially absorbed in the markup of an imperfectly competitive firm. Hooper and Mann (1989) allow for the possibility that
over time markups gradually return toward their desired levels so that
pass-through slowly builds up over time. They confirm this empirically
in finding a short-run pass-through of 20% increasing to 60% in the long
run.
Our model yields similar results. Defining the markup as M =
[frac{xp}{c}], with c = c([w.sub.D],[x.sub.t][w.sub.F]), we find from
Equations 9 and 10 and the homogeneity of the indirect cost function
that
[frac{[partial]M}{[partial]x}] = [frac{(a/2b) + [[p.sub.0] -
(a/2b)][e.sup.-[lambda][c.sup.t]]}{c[([w.sub.D]/x,
[w.sub.F]).sup.2]([w.sub.D]/[x.sup.2])[c.sub.1]([w.sub.D]/x,
[w.sub.F])}] [greater than] 0 (11)
since both numerator and denominator are positive. Note that
partial derivatives are denoted by a numerical subscript indicating the
function argument. It is easy to derive from Equation 11 that
sgn [frac{[partial]([partial]M/[partial]x)}{[partial]t}] = sgn
[frac{[partial]([partial]M/[partial]x)}{[partial][lambda]}] = sgn
[([frac{a}{2b}]) - [p.sub.0]] [less than] 0. (12)
For a feasible initial price, [p.sub.0] [greater than]
[frac{a}{2b}], the absorption of the exchange rate change in the profit
margin diminishes over time, implying increasing pass-through as time
progresses. In addition, the initial absorption of the exchange rate
change in the profit margin is less when the speed of price adjustment
is lower.
4. Data and Empirical Methodology
Data on U.S. export prices by commodity are obtained from the
Bureau of Labor Statistics (BLS). These data start in the third quarter
of 1978 at the earliest and in the last quarter of 1994 at the latest.
Data for most commodities end in December 1995. Eliminating the series
with less than 10 years of data together with several other selection
criteria produces time series of prices for a set of 31 commodities. [4]
We use quarterly data, although part of the series is monthly. All the
price data in the estimation are expressed in U.S. dollar terms. We
divide the price data by the U.S. consumer price index (CPI) to obtain
the real price. The BLS does not indicate the destination or source
countries for the traded commodities. Accordingly, we cannot use
bilateral exchange rates but instead use the real trade-weighted
exchange rate index available from Citibase.
In order to illustrate how to test implications (iv) and (v), which
relate the speed of price adjustment to the commodity-specific discount
rate and the commodity-specific demand curve, we obtained the following
data for a preliminary analysis. To capture the discount rate
appropriate for the commodity under consideration, we consider the
average stock return by commodity. The average stock returns include a
risk premium that is thus estimated using a theory-free approach. That
is, we are not required to specify a specific risk model (such as the
Capital Asset Pricing Model [CAPM]). Data on the rates of return on
equity for the industries examined here are obtained from Compustat.
From the international trade price code numbers provided by the BLS, we
obtain the best-matching standard industrial classification code
numbers. [5]
As a debatable proxy for the slope of the demand curve, we use the
Herfindahl index: Less competitive firms may have lesser demand slope b
and also may be in more concentrated industries with a higher
"Herfindahi index" number. [6] Feinberg (1986) previously
employed the Herfindahl index to represent concentration in the context
of explaining differences in degree of pass-through across industries.
For each industry, the Herfindahi index for this study is obtained from
the Census of Manufactures of the U.S Department of Commerce. Since no
data are available on the quantity adjustment cost parameter, we assume
that this parameter is held constant across industries.
Given the presence of a lagged endogenous variable, we must
transform the data to correct for serial correlation, if present, as
ordinary-least-squares (OLS) estimates would otherwise be inconsistent.
[7] The legitimate application of OLS on the transformed data requires
that all series be stationary and, more restrictively, that the errors
be free of serial correlation. We find that we can reject
nonstationarity on the transformed data for all commodity price series
and the trade-weighted real exchange rate index using Dickey-Fuller
tests. After we obtain the estimates of the speed of price adjustment
[lambda] for each commodity from the transformed data, we may regress the [lambda]'s on the foreign demand slope and discount rate
proxies by OLS. [8]
5. Preliminary Estimation Results and Interpretation
The following equation is estimated with time series data on 31
commodities exported from the United States:
[p.sub.ti] = [[alpha].sub.i] + [[beta].sub.i][p.sub.t-1i] +
[[gamma].sub.i] [frac{1}{[x.sub.t]}] + [e.sub.i]. (13)
Note that c([w.sub.D]/[x.sub.t], [w.sub.F]) is approximated by
1/[x.sub.t], (and the constant), which represents a first-order
approximation that is reasonable if the input prices are not too
strongly correlated with the other right-hand-side variables in the
regression.
Table I shows that the coefficients [[beta].sub.i], [[gamma].sub.i]
both are significantly positive for the majority of the commodities,
supporting implications (i) and (ii) of the model. More precisely, since
[[lambda].sub.i] = 1 - [[beta].sub.i], the price adjustment coefficient
is significantly below one for 18 of the 31 commodities (and not
significantly different from one in all other cases). Further,
[[gamma].sub.i] is significantly positive in 25 out of 31 cases,
implying that a real appreciation of the dollar typically raises the
foreign currency price of U.S. exports as expected. The average values
for all commodities are [lambda] = 0.76 and [lambda] = 0.62.
The point exchange rate elasticities of the product rice differ by
quarter because of variation in the x/p ratio. To obtain a general
picture, we calculate the point elasticities for all time periods
available in the data set. We then delete the five lowest and highest
point elasticities to avoid outliers and calculate the averages for each
commodity. Table 2 reports the means and standard deviations of the
point elasticities of the trade prices with respect to the exchange
rate. Notice that the short-run point elasticity equals [eta](s) =
[dp/d(1/x)][(1/x)/p] [lambda]/px in Equation 13, while the long-run
point-elasticity is found as [eta](l) = [eta](s)/[lambda]. Most
industries respond in less than full proportion in the short run, with a
mean elasticity of 0.81. The mean long-run elasticity equals 1.07 (but
falls slightly below one if 5% of the outliers are removed on both
sides). [9]
The Durbin h-statistics in Table 1 show that significant
correlation remains after transformation in 11 out of 31 cases (critical
Durbin h of [pm] 1.96 at the 5% level). These cases are generally those
commodities for which we find immediate price adjustment. To confirm
implication (iii), we obtain the correlation between the
[[lambda].sub.i] and [[gamma].sub.i], which is significantly positive as
predicted, p([lambda], [gamma]) = 0.66. If we consider only those
commodities with an acceptable Durbin h-statistic, we find that
p([lambda], [gamma]) = 0.89.
In the second stage of the empirical analysis, we regress the
speeds of price adjustment for the exported commodities on the proxies
for the discount rate and the price responsiveness. Based on Equation 4,
assuming a constant adjustment cost cross sectionally, the speed of
price adjustment theoretically depends negatively on the discount rate
(implication [iv]), and positively on the slope of the foreign demand
curve (implication [v]). Results are presented here for the sake of
illustration since the use of questionable proxies (to some extent, the
average stock returns by commodity representing discount rates but in
particular the Herfindahl index as a proxy for the slope of foreign
demand) makes these results tentative at best:
[[lambda].sub.i] + [c.sub.0] + [c.sub.1][Herf.sub.i] +
[c.sub.2][Rate.sub.i] + [Error.sub.i].
Table 3 reports the illustrative regression result based on
Equation 14. The sign of the rate variable is negative as predicted with
significant t-statistic of 2.79, thus illustrating implication (iv). The
estimated coefficient for the Herfindahl index equals 0.00, not
statistically significant (t-statistic = 0.09), so that implication (v)
is not confirmed in this illustration.
6. Conclusion
The motivation for our paper is twofold. First, it adds a dynamic
element to the traditional pass-through analysis, which is mainly static
in nature, except for Dixit (1989). Second, more generally, we take a
small step toward taking advantage of the exchange rate variability in
the post-Bretton Woods era, which makes international trade a perfect
arena from which to study price rigidity. By assuming a quantity
adjustment cost, we are able to derive a theoretical link between price
adjustment speed, the dynamics of the markup, and pass-through.
We find that pass-through increases over time, if price adjustment
is noninstantaneous, and increases in the speed of price adjustment;
thus, the theoretical covariance between pass-through and price
adjustment speed is positive. Further, the speed of price adjustment
and, accordingly, the degree of pass-through in the short run, depend on
the slope of the demand curve, the discount rate, and the quantity
adjustment cost parameter.
Empirically, we find that in response to, say, a 10% change in the
exchange rate, passthrough in U.S. export prices for 31 commodities
equals 8.1% on average in the short run, increasing eventually to about
10%. Although the degree of rigidity in the aggregate does not appear to
be as important economically as was found in some previous studies, a
significant degree of rigidity is found in the majority of the sectors
we investigate. We also find that the correlation coefficient across the
industries between the degree of pass-through and price adjustment speed
is significantly positive in the range of 0.6 to 0.9.
The substantial variation in pass-through elasticities as presented
in Table 2 indicates that the effects of exchange rate changes are not
uniform across industries. A currency depreciation will thus have
different effects on different industries. Industries appear to cope
with exchange rate changes in different ways, and there may be serious
distribution effects of currency adjustments.
The results presented here for the adjustment cost view must be
interpreted cautiously. Our partial equilibrium approach takes the
exchange rate as exogenous and, for example, does not allow for mean
reversion in exchange rates that, if present, must surely affect price
setting in our adjustment-cost environment. We further assume a linear
demand curve and ignore potential strategic interactions within
industries. We do not distinguish empirically between export
destinations and so cannot address the issues of price discrimination
raised by Knetter (1989). Inability to distinguish export destinations
also decreases the reliability of our price adjustment tests since trade
weights of specific commodities change significantly over time.
Our model, however, has provided some insights into the dynamics of
pass-through. We expect that key results--related, for example, to the
correlation between price adjustment speed and exchange-rate
sensitivity--and the effect of discount rates on price adjustment speed
and short-run pass-through will survive in a more complex framework.
(+.) Department of Economics, Lingnan University, Tuen Mun, Hong
Kong.
(*.) Department of Economics, West Virginia University, Morgantown,
WV 26506, USA; E-mail rbalvers@wvu.edu; corresponding author.
The authors thank two anonymous referees, Subhayu Bandyopadhyay,
and Yangru Wu for helpful comments and suggestions.
(1.) The relationship between local currency import prices (or the
foreign export prices denominated in the currency of the importing
country) and exchange rates has been referred to as the
"pass-through" relationship in the literature. If a less than
proportional relationship between import prices and exchange rates
holds, pass-through is said to be incomplete.
(2.) To the extent that the foreign competitors' costs are
also affected by the exchange rate (if they use the other country's
inputs), they may adjust their prices as the exchange rate changes,
which would affect the demand curve in Equation 2. However, the natural
presumption is that their costs will be affected less than the domestic
firm producing for export so that qualitative results will continue to
hold.
(3.) The implications of other adjustment cost formulations are
quite similar to those of the quantity adjustment formulation considered
here. If adjustment of (real) prices is costly, implications (i) to (iv)
will continue to bold, but the sign of (v) is reversed. Motivations for
such costs relate to future profit losses resulting from large real
price changes that antagonize customers and hurt the reputation of the
firm (Okun 1981; Rotemberg 1982), increase risk (Greenwald and Stiglitz
1989), or lower the precision of demand forecasts (Balvers and Cosimano
1990). Note that each of these explanations rests on price changes as
measured in the currency of the importing country. If quantity
adjustment costs stem from, say, the costs of hiring and firing labor
instead of stemming from bottlenecks as trade levels change in a
particular market, then the adjustment costs occur in the domestic
currency instead of the relevant foreign currency. Implications from
this formulation are equivalent to those obtained previ ously, with the
addition that the speed of price adjustment now depends (positively) on
the real exchange rate. These results are available from the authors on
request.
(4.) The exact criteria for selecting the set of commodities
examined are as follows. First, we use all data sets available from the
BLS Web site that have a time series of at least 10 years. Second, we
choose the data at the most disaggregate five-digit international price
code level. Third, we exclude all industries under the SIC code numbers
for which the Herfindahl index is not available. Finally, we exclude all
industries under a particular SIC code number for which the data on
rates of return are not available from Compustat. Applying these
selection criteria, we end up with 31 sets of commodities with export
price data from an original total of 141 sets of commodities on the BLS
Internet site.
(5.) "Census of Manufactures" issued February 1992 by the
U.S. Department of Commerce provides the corresponding SIC code number
for given BLS code numbers. If the match is not perfect, we use a range
of SIC codes.
(6.) Our use of the Herfindahl index as a proxy for the slope of
the demand curve is questionable for several reasons. First, since
market demand slopes vary by industry, two industries that are equally
concentrated will likely have different demand slopes. Second, there may
not be a close correlation between an industry's concentration in
the United States (as measured) and that abroad (as needed theoretically). Third, the SIC categorization defining the industries
need not represent a good characterization of the true market in which
the firm operates.
(7.) Using the Durbin h-test, we find significant serial
correlation in all cases. To correct for serial correlation, Harvey
(1990), Maddala (1992), Greene (1993), and others suggest choosing the
lagged value of one of the exogenous right-hand variables, in our case
[x.sub.i-1] to instrument for the lagged endogenous variable, in our
case [p.sub.i-1]. Since x is exogenous to any industry, [x.sub.i-1] is,
by definition, uncorrelated with the error so that the conditions
necessary for consistency are satisfied. The structure of the model
ensures that [x.sub.i-1] will show a reasonably high degree of
correlation with [p.sub.i-1]. Thus, we perform instrumental variable
estimation to obtain the parameter values p for the degree of
first-order serial correlation to be used in transforming the data.
(8.) This two-step procedure is preferred over estimating Equation
9, with the equation for [lambda] related to Equation 4 substituted in,
directly in one step: The estimate of [lambda] is consistent directly
from time-series Equation 9, even though additional cross-sectional
information exists that theoretically could improve the estimate.
However, using the cross-sectional information directly would require
one of two compromises: either the more exact multiplicative formulation
would be maintained so that the variables explaining [lambda] would
enter multiplicatively with the lagged price and the real exchange rate
(this would likely cause serious multicollinearity problems) or the
expression would be linearized without interaction variables, in which
case the estimate of the lagged price coefficient or any inferred
estimate of [lambda] would become inconsistent.
(9.) The linear demand assumption implies that the price elasticity
is decreasing in price and implies incomplete pass-through in the long
run. If we assume constant elasticity of demand, we cannot solve the
model analytically for the price dynamics. However, the steady-state
price moves proportionately with the exchange rate so that pass-through
is complete in the long run. We speculate that pass-through would be
incomplete in the short run for constant elasticity of demand: If an
exchange rate depreciation implies a proportionate price increase in the
long run and an associated decrease in production, then, because of the
quantity adjustment costs, production decreases slowly over time toward
the decreased steady state. During the adjustment, however, quantity is
above and, accordingly, price below its steady state, so the
pass-through is incomplete in the short run. Our empirical results of a
0.81 short-run elasticity becoming 1.0 in the long run thus appears to
be most consistent with a constant-elasticit y formulation. Several of
the long-run elasticities in Table 2 are significantly above one. Such
outcomes would he expected when demand curves are more convex than under
constant elasticity.
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Appendix
Derivation of the Model Solution
The model of Equations 1 and 2 in the text implies the following
value function:
J(q, x, t) = [frac{max}{[[{u}.sup.[infty]].sub.t]}] E [[[integral
of].sup.[infty]].sub.t] [e.sup.-rs][xpq - cq - [frac{1}{2}][xhu.sup.2]]
ds, (A1)
defining q' = u and setting for simplicity c([w.sub.D],
X[w.sub.F]) = c. The Bellman equation becomes
-[J.sub.3](q, x, t) = [max.sub.u] [[e.sup.-rt](xpq - cq -
[frac{1}{2}][xhu.sup.2]) + [J.sub.1](q, x, t)u], (A2)
subject to Equation 2, where numerical subscripts indicate partial
derivatives. The optimal choice of u implies that
u = [e.sup.rt][J.sub.1]/hx.
Next, guess a functional form for the value function
J = [e.sup.-rt][A[q.sup.2]x + Bqx + Cq + D/x + Fx + G],
Where A, B, C, D, F and G are constants to be determined. Obtaining
[J.sub.1] and [J.sub.3] from Equation A4 and u from Equation A3 and
substituting into Equation A2 implies the following restrictions on the
constants:
rA = -(1/b) + 2[A.sup.2]/h (A5)
rB = (a/b) + 2AB/h (A6)
rC = -c + 2AC/h (A7)
rD = [C.sup.2]/2h (A8)
rF = [B.sup.2]/2h (A9)
rG = BC/h. (A10)
Clearly, our guess for the form of the value function can be
verified. For the control variable from Equation A3 and A4 we have
u = q' = [2Aq + B + (C/x)]/h. (A11)
Solving the first-order differential equation in Equation All for q
produces
[q.sub.t] = [[q.sub.0] + [frac{B + (C/x)}{2A}]][e.sup.(2A/h)r] -
[frac{B + (C/x)}{2A}]. (A12)
Thus, to obtain the explicit solution, we need only solve for A, B,
and C. From Equation A5, we find that
A = [rh - [([r.sup.2][h.sup.2] + 8h/b).sup.1/2]]/4, (A13)
where we have taken the negative root, which ensures convergence.
Using the solution for A, it is easy from Equation A6 and A7 to solve
for B and C as well.
Substituting the solutions for A, B, and C into Equation A12 and
employing Equation 2 to convert quantity into price produces Equations
3, 4, and 5 in the text as desired.