This paper addresses the fundamental question of whether, in a comparative-advantage context, the gains from trade will be greater when the differences between trading countries are greater. Such a presumption is established. The paper then discusses circumstances that could cause the presumption to fail.trade gains, international differences

Wilfred J. Ethier

English

Research Papers in Economics

 
 
WP 001‐08  JULY 2008 
First version: 30 November 2007 
This printing: 2 March 2008 
The Greater the Differences,  
the Greater the Gains? 
Wilfred J. Ethier 
Department of Economics 
University of Pennsylvania 
The International School of Economics at Tbilisi State University (ISET) is supported by 
BP, the Government of Georgia, the Norwegian Ministry of Foreign Affairs, Higher 
Education Support Program of the Open Society Institute, the Swedish International 
Development Agency and the World Bank. 
International School of Economics at Tbilisi State University 
16 Zandukeli Street, Tbilisi 0108, Georgia 
www.iset.ge    e‐mail:  publications@iset.ge 
 
I IS SE ET T  WORKING PAPER SERIES The Greater the Differences, the Greater the
Gains?
Wilfred J. Ethier 
Department of Economics tel: 215–898–5105
University of Pennsylvania fax: 215–573–2072
Philadelphia, PA 19104–6297 email: ethier@econ.sas.upenn.edu
Abstract: This paper addresses the fundamental question of whether, in a comparative-advantage
context, the gains from trade will be greater when the differences between trading countries are greater.
Such a presumption is established. The paper then discusses circumstances that could cause the
presumption to fail.
Keywords: trade gains, international differences
JEL Classification Codes: D60, F13, H20
Outline: 
I .  I n t r o d u c t i o n . .................................................................. 1
I I .  T h e   F r a m e w o r k ................................................................ 2
I I I .  A n a l y s i s . .................................................................... 5
I V .  D i s c u s s i o n .................................................................... 6
V .  C o n c l u d i n g   R e m a r k s . ........................................................... 9
R e f e r e n c e s ......................................................................... 1 0This paper exists because of the stimulation provided by Kemp and Tran-Nam (2008). I thank Roy Ruffin for
*
helpful comments.
The Greater the Differences, the Greater the
Gains?
Wilfred J. Ethier
*
University of Pennsylvania
Comparative-advantage trade is, at bottom, trade to exploit differences between
countries. This paper addresses the fundamental question of whether the gains from
such trade are greater if the differences between countries are greater.
I. Introduction
In the late 1970s and early 1980s trade theorists devoted much effort to developing
non-comparative-advantage models featuring economies of scale and imperfect
competition. This development was explicitly motivated by accumulating empirical
evidence emphasizing that the larger part of world trade consisted of the exchange of
(relatively similar) manufactures between (relatively similar) industrial countries. One
often heard statements like, “Comparative-advantage trade is trade to exploit differ-
ences, so this can’t be comparative-advantage trade.”
Such statements were nonsense (I mercifully abstain from citations). It is true that,
in a comparative-advantage world, if autarky relative prices do not differ much acrossThe Greater the Differences, the Greater the Gains? Page 2
countries, trade can produce only modest relative-price changes in each country. But
such modest changes can induce large trade volumes if import price-elasticities are
high enough, and it is exactly with trade between similar countries that we would
expect elasticities of substitution (and so import elasticities) to be the highest.
To our students we usually then say something like: “But it still matters whether
this trade is due to comparative advantage rather than to something else. While
comparative advantage need not imply ‘the greater the differences, the greater the
trade,’ it does suggest ‘the greater the differences, the greater the gains.’ This
suggests that the more important consequences of trade policies are those impacting
trade between dissimilar countries, even though that may be a smaller part of world
trade. But if this trade is due to something other than comparative advantage, all bets
are off.”
But we can point our students to no formal proposition addressing the statement in
italics! Instead we may present a few (well-chosen, we hope) examples. Such a
proposition should be a fundamental part of comparative-advantage trade theory,
comparable in importance to the comparative-advantage theorem itself.
II. The  Framework
I would like to address the issue of the greater the differences, the greater the gains
(GD–GG) in a framework of general differences, though confined of course to a
comparative-advantage context. Suppose a two-country, two-good, comparative-
advantage world (perfect competition, no externalities) with a free-trade equilibrium
described by:
M ( P ,   á ) = X*(P, á)(1)
where  M is home excess demand for good B, X* foreign excess supply, and P the
free-trade relative price of B in terms of A. Designate the country with the compara-Wilfred J. Ethier Page 3
tive advantage in A as the home country (so that M and X* are positive). The vector á
encompasses all parameters determining the degree of comparative advantage of the
two countries: endowments, technology parameters, taste parameters, relevant
government policies.
With so many parameters, it’s desirable to restrict parameter changes in some way
to ensure that comparisons are meaningful. A natural point of reference is a given
free-trade equilibrium (1). So, consider the set of all possible changes dá that satisfy:
áá M   C   d á  =  X*   C   d á (r1)
and
de + de* = 0. (r2)
Here e and e* denote home and foreign expenditure in the free-trade equilibrium. So
r1 and r2 restrict attention to parameter changes that leave the world relative price
and the world income (but not the international distribution of that income) un-
changed in the free-trade equilibrium. The reason for (r2) is that a change in the size
of the world economy would itself change the gains from trade, independently of
whether the countries had become less alike or not. The role of this constraint will be
discussed later. The basic idea is to start with a given free-trade equilibrium and then
ask whether the gains that that equilibrium generates are greater the greater the
differences in the countries that are trading.
Consider only dá that satisfy both r1 and r2.(R)
With the point of reference thus set, the next step is to specify what is meant by
“greater differences” (GD). I think that, in a comparative-advantage setting, the
compelling candidate is simply autarky price differences. Autarky prices are given by
0 0 M ( P ,  á) = 0 = X*(P *, á). (2)
00 Since the home country has the comparative advantage in A, P  >  P *. So a parameter
change can be said to produce greater differences between the two countries if:The Greater the Differences, the Greater the Gains? Page 4
00 d á  implies that dP  >  dP *. (GD)
Finally I must specify what I mean by “greater gains” (GG). Measure the global gains
from trade in the following conventional way.
00 0 0 G  = e + e* – (Pb   + a ) – (Pb *  + a *). (3)
0 Here b  etc. refer to autarky production (= consumption) of the respective goods in the
respective countries. If G is positive, world income with free trade is more than
sufficient, at free trade prices, to purchase the world autarky consumption bundle.  By
“greater gains” I mean simply that G increases.
d á  implies that dG > 0. (GG)
So, my criterion is that, globally, gainers gain more than losers lose. This is
analogous to the basic gains-from-trade proposition of comparative advantage that, in
each country, gainers gain more (strictly: not less) from trade than losers lose. Of
course the literature has gone beyond that to investigate the existence of a lump-sum
transfer scheme that would produce a Pareto improvement [see Kemp (1962),
Samuelson (1962), Grandmont and McFadden (1972), and Kemp and Wan (1972)].
Also, Dixit and Norman (1980, pp 79, 80) have demonstrated the use of commodity
and factor taxes and subsidies to generate a Pareto improvement. Analogously, I could
now also ask what further restrictions on R might guarantee that all individuals gain,
not just the world as a whole (while ruling out international lump-sum transfers). But
I instead investigate only the more basic issue.Wilfred J. Ethier Page 5
III. Analysis
So, now the stage is set to pose the basic question: When must a dá consistent with R
and implying GD necessarily also imply GG? A preliminary answer comes fairly
easily.
From (2),
p0 p , since these expressions are evaluated at autarky where income   > 0 > M * *0 Now,  X
00
effects wash out. Impose the following.
á Assumption 1 Given dá, M  C dá has the same sign over all P for which M $ 0,
á and X*  C dá has the same sign over all P for which X* $ 0.
áá Now,  r1 requires M  C dá to have the same sign as X*  C dá, in the initial free-trade
equilibrium, and Assumption 1 ensures that this will be the same sign as that of
áá M   C   d á  and X*  C dá. Because of the assumed pattern of comparative advantage,
00
00 áá 0 P  >  P *. If the signs of M  C dá and X*  C dá are both positive, dP  < 0 and
00
0 dP * > 0, by (4), whereas both signs being negative gives the opposite result. Thus, a
00 d á , consistent with R, causes GD with dP  > 0 and dP * < 0, given Assumption 1, if it
causes both terms to be negative.
So, given GD, differentiate (3):
The first equality in (5) follows from r2 and the second from the production envelope
theorem valid in comparative-advantage models.
(4)
(5)The Greater the Differences, the Greater the Gains? Page 6
00 The terms (P  – P) and (P – P *) are both non-negative, with at least one strictly
positive, since the home economy has a comparative advantage in A. Production
00 0 0 substitution in a comparative-advantage world implies that db /dP  and db */dP * are
both positive (assuming we are not confined to an endowment model). Finally, r1 and
00 Assumption 1 give GD with dP  > 0 and dP * < 0. Thus dG > 0.
Proposition 1 Given Assumption 1, any dá consistent with R that implies GD
also implies GG.
Proposition 1 establishes a “presumption” that, indeed, the greater the differences, the
greater the gains.
IV. Discussion
Proposition 1 gives only a presumption because it depends upon Assumption 1 and,
also, on how the problem is defined by R. In particular, the requirement r2 restricts
the domain of relevance of Proposition 1. This section addresses circumstances that
could cause the presumption to fail.
We clearly have an opportunity for counterexamples to GD–GG if we dispense
with Assumption 1. Assumption 1 basically says that the parameter change should
shift the import-demand (export-supply) curve unambiguously in one direction or
another. This is true in most of the standard exercises. But sufficient inferiority in
consumption could produce violations. Suppose, for example, that imports are very
inferior. Then a parameter change that caused an economy to want to import more
near autarky, where income effects basically wash out, might cause it to want to
consume less in free trade, with significant income effects.
Figure 1 illustrates how a failure of Assumption 1 might vitiate the presumption.
The initial equilibrium is at E with free-trade relative price PN. The parameter changeWilfred J. Ethier Page 7
dá shifts the initial M and X* schedules to MN and X*N, respectively, with the
equilibrium moving to EN. The free-trade price remains at PN, as required by (R). Both
00 autarky prices rise, but P  rises more than P *, so (GD) is satisfied. This is possible
because X* shifts to the left near autarky but to the right with a higher volume of
trade. Foreign inferiority in the consumption of B could cause this: Near autarky the
income gain from trading more could raise foreign consumption of B, leaving less for
export, whereas at the higher income levels produced by larger trade gains foreign
consumers purchase less of the inferior B, leaving more for export. The last two terms
on the right-hand side of (5) now work to cross purposes, and the last term will
00 dominate if P – P * is large enough relative to P  – P, that is, if trade is sufficiently
more valuable to the foreign economy than to the home economy. (The figure shows 
00 P – P * larger than P  – P).
 Anyway, Assumption 1 is only a sufficient condition, not a necessary one. So the
suggestion is that while counterexamples are unlikely to be important, they do exist,
and they would likely (but not necessarily) involve significant inferiority in consump-
tion. This is consistent with the message delivered by Kemp and Tran-Nam (2008).The Greater the Differences, the Greater the Gains? Page 8
Perhaps more interesting, though, is the role played by R, especially by r2. Note
that, if de + de* > 0, the above logic is not affected (indeed, reinforced), so that the
Proposition still holds. Thus r2 can be generalized to de + de* $ 0.
So, suppose that a dá, consistent with r1 and implying GD, also implies that 
de + de* < 0. In this case, the above logic still implies that, with GD, the world does
gain relative to the initial free-trade world income, but that the actual free-trade world
income falls, leaving the net gain from trade indeterminate.
A concrete example might help here. Suppose a textbook Heckscher-Ohlin-
Samuelson world with two countries that, except for endowments, are identical,
including identical homothetic tastes. Suppose that with free trade both countries are
in a common free-trade diversification cone. Then a transfer of capital from one
country to the other, provided it leaves both in the diversification cone, clearly
satisfies R. So no problem. Consecutive transfers of capital from the labor-abundant
country to the capital-abundant one, making the two countries more dissimilar,
consecutively increase the gains from trade, as long as both countries remain in the
diversification cone.
But when at least one country leaves that cone, the free-trade equilibrium will
feature specialization by at least one country. Then a further transfer of capital from
the labor-abundant country to the capital-abundant one, which would increase even
more the international disparity in relative factor endowments, would now also shift
capital from where its marginal product is relatively high to where it is relatively low,
thus lowering world income with free trade at the initial P. On balance, the net gain
from trade could either rise or fall.
The moral seems to be that, if free trade features specialization, trade has not been
sufficient to counteract completely the effect of national borders. Thus making
countries even more dissimilar accentuates the negative effect of those borders in the
trading equilibrium. This is a significant qualification to the GD-GG presumption,
probably much more important than counter-examples involving departures from
Assumption 1. And r2 is very useful in exposing the argument.
Understanding the qualifications to the presumption facilitates a judgment about
when it is most likely to be pertinent. For example, trade between rich countries tends
to feature substitution effects that are strong relative to income effects and muchWilfred J. Ethier Page 9
diversification in national production. So the presumption established by Proposition
1 can be expected to be high in this context.
V. Concluding  Remarks
I have addressed the fundamental question of whether, in a comparative-advantage
context, the gains from trade will be greater when the differences between trading
countries are greater. When the question is formalized in what I regard as the natural
way, such a presumption does hold. Two sets of circumstances could cause the
presumption to fail: large income effects relative to substitution effects combined
with significant inferiority in consumption, and specialization in production under
free trade.The Greater the Differences, the Greater the Gains? Page 10
References
Dixit, A. K. and V. Norman, 1980, THEORY OF INTERNATIONAL TRADE (Cam-
bridge, UK: Cambridge University Press).
Grandmont, J. M. and D. McFadden, 1972, “A Technical Note on Classical Gains
from Trade,” JOURNAL OF INTERNATIONAL ECONOMICS 2, pp 109–125.
Kemp, M. C., 1962, “The Gain from International Trade,” ECONOMIC JOURNAL 72,
pp 803–819.
Kemp, M. C. and H. Y. Wan, 1972, “The Gains from Free Trade, “ INTERNATIONAL
ECONOMIC REVIEW. 13, pp 509–522.
Kemp, M. C. and B. Tran-Nam, 2008, “Do Trade Gains Increase with Increases in
International Disparities in Factor Proportions?” In: Kamihigashi, T. And L. Zhao
(eds.), INTERNATIONAL TRADE AND ECONOMIC DYNAMICS: ESSAYS IN MEM-
ORY OF KOJI SHIMOMURA (NY: Springer), forthcoming.
Samuelson, P. A.,1962, “The Gains from International Trade Once Again,” ECO-
NOMIC JOURNAL 72, pp 820–829.

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