International Economics
Li Yumei
Economics & Management School
of Southwest University
International Economics
Chapter 2
The Law of Comparative
Advantage
Organization
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2.1 Introduction
2.2 The Mercantilists’ View on Trade
2.3 Trade Based on Absolute Advantage:
Adam Smith
2.4 Trade Based on Comparative Advantage:
David Ricardo
2.5 Comparative Advantage and Opportunity
Costs
2.6 The Basis for and the Gains from Trade
Under Constant Costs
2.7 Empirical Tests of the Ricardian Model
Chapter Summary
Exercises
2.1 Introduction

Historical Approach to Examine the
Development of International Trade
Theory (Mercantilism, Absolute
Advantage, Comparative Advantage)

Three Basic Questions

Basis for Trade

Gains from Trade

Patterns of Trade
2.2 The Mercantilists’ View on
Trade
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Early Mercantilists
Main Views on Trade
Comments
Conclusion
Some Mercantilism Data
 Early Mercantilists
Mercantilism
Mercantilism was established during the early modern period (starting in
the 16th to the 18th century, which roughly corresponded to the
emergence of the nation-state) .
Mercantilism is an economic theory that holds the prosperity of a nation
depends upon its supply of capital, and that the global volume of trade
is “unchangeable.” Economic assets, or capital, are represented by bullion
(gold, silver, and trade value) held by the state, which is best increased
through a positive balance of trade with other nations (exports minus
imports). Mercantilism suggests that the ruling government should
advance these goals by playing a protectionist role in the economy, by
encouraging exports and discouraging imports, especially through the
use of tariffs. The economic policy based upon these ideas is often
called the mercantile system.

 Early Mercantilists
Early Mercantilists
The Early Mercantilists: Thomas Mun (1571–1641), Edward Misselden
(1608–1634) And Gerard De Malynes (1586–1623)

Thomas Mun(1571-1641)
- Representative Works
England’s Treasure by Foreign Trade published in 1664
- Experiences
Thomas Mun , English Writer on Economics, was the third son of John
Mun, mercer of London. He began by engaging in Mediterranean trade,
and afterwards settled down in London, amassing a large fortune . He
was a member of the committee of east India company and of the
standing commission on trade appointed in 1622 . In 1621 Mun

published A Discourse of Trade from England unto the East Indies
 Main Views on Trade
Why do nations trade?
zero-sum gain—one nation gains at the expense of the other

Main Views on Trade
The Mercantilist School common outlook:
(1) the idea of specie or bullion as the essence of wealth
(2) the notion that a positive balance of trade (trade surplus) is an index
of national welfare.
(3) It is also associated with an emphasis on population growth and low
wages, a concern with full employment
(4) zero-sum gain — one nation gains at the expense of the other ,
denying foreign trade as a source of net gain to the world as a whole.
(5) A permanent balance of trade surplus should be beneficial to a nation
has been a source of discussion right down to the present day.
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 Comments



Mercantilism led to some of the first instances of significant
government intervention and control over market economies, and
it was during this period that much of the modern capitalist system
was established.
Internationally, mercantilism encouraged the many European wars
of the period, and fueled European imperialism, as the European
powers fought over “available” markets.
Mercantilism developed at a time when the European economy
was in transition (Feudalism to capitalism)
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

One single economic ideology
Static view of the world economy
The wealth of a nation measured by the stock of precious metals it
possessed, while at present by its stock of human, man-made, and
natural resources available for producing goods and services.
 Conclusion

Early mercantilist writers embraced bullionism, the belief
that that quantities of gold and silver were the measure of
a nation’s wealth. Later mercantilists developed a
somewhat more sophisticated view.

Many European economists between 1500 and 1750 are
today generally considered mercantilists .

“Mercantilist Literature” appeared in the 1620s in Great
Britain.

Economic Nationalism

Belief in mercantilism began to fade in the late 18th
century, as the arguments of Adam Smith and the other
classical economists won favour in the British Empire
 Mercantilism Data
Exports of 'Treasure' and Merchandise to India By the
British East India Company, in Pounds Sterling, Decennial
Means, 1660-69 to 1710-19

Decade Treasure %
Merchandise % Total in �
1660-69 74,022.4 64.3%
41,085.2 35.7% 115,107.6
1670-79 234,091.4 72.2%
89,990.8 27.8% 324,082.2
1680-89 383,707.7 87.2%
56,170.2 12.8% 439,877.9
1690-99 166,561.4 69.8%
72,065.2 30.2% 238,626.6
1700-9 337,008.9 84.7%
60,876.5 15.3% 397,885.4
1710-19 371,418.1 79.2%
97,771.3 20.8% 469,189.4
Exports of Gold and Silver 'Treasure' to India By the
British East India Company in Pounds Sterling
Decade Silver Percent Gold Percent
1660-69 51,446.7 69.5% 22,575.7 30.5%
1670-79 102,038.1 43.6% 132,053.3 56.4%
1680-89 262,870.4 68.5% 120,837.3 31.5%
1690-99 163,230.2 98.0% 3,331.2
2.0%
1700-09 325,887.6 96.7% 11,121.3 3.3%
1710-9 369,340.3 99.4% 2,077.8
0.6%

Total Value
74,022.4
234,091.4
383,707.7
166,561.4
337,008.9
371,418.10
2.3 Trade Based on Absolute
Advantage: Adam Smith
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Absolute Advantage
Illustration of Absolute Advantage
Main Views on Trade
Comments
Conclusion

 Absolute Advantage
Adam Smith(1723-90)
Absolute advantage theory was proposed by Adam
Smith (1723-90) . With The Wealth of Nations Adam
Smith installed himself as the fountainhead of
contemporary economic thought . Adam Smith was born
in a small village in Kirkcaldy, Scotland. There his
widowed mother raised him until he entered the University of Glasgow at
age fourteen, as was the usual practice, on scholarship. He later
attended Balliol College at Oxford, graduating with an extensive
knowledge of European literature and an enduring contempt for English
schools. He returned home, and after delivering a series of well-received
lectures, was made first chair of logic (1751), then chair of moral
philosophy (1752), at Glasgow University.
Adam Smith (1723-90)
He left academia in 1764 , his famous works” The Wealth of
Nations” was published in 1776, the same year the American
Declaration of Independence was signed and in which his close
friend David Hume died. In 1778 he was appointed commissioner
of customs. This job put him in the uncomfortable position of
having to curb smuggling(走私活动), which, in The Wealth of
Nations, he had upheld as a legitimate (正当合理的) activity in the
face of "unnatural" legislation. Adam Smith never married. He died
in Edinburgh on July 19, 1790.
An Inquiry into the Nature and Causes of the Wealth of Nations
(Wealth of Nations)
Attack on the Mercantilism
By the eighteenth century, the economic policies of the mercantilists were
under strong attack.
1. David Hume’s price-specie-flow doctrine(1711-1776) :
A favorable trade balance was possible only in short run,
for over time it would automatically be eliminated.
trade surplus →inflow of gold and silver→ the increase
of money circulation →relatively higher price of that
trading partner →more purchased foreign-produced
goods for domestic consumers→ the decline of
exports→ the elimination of trade surplus
2. Adam Smith
Mercantilists’ static view of the world economy (constant size of the
world’s economic pie or zero-sum game) was attacked by Adam Smith
(mutually beneficial game). (industrial revolution from 1760 to 1832 )

 Absolute Advantage
Introduction
Adam Smith coined (创新) the term "mercantile system" to describe the
system of political economy that sought to enrich the country by
restraining imports and encouraging exports. This system dominated
western European economic thought and policies from the sixteenth to the
late eighteenth century. The goal of these policies was, supposedly, to
achieve a "favorable" balance of trade that would bring gold and silver into
the country. In contrast to the agricultural system of the physiocrats(自然
拥护者), or the laissez-faire of the nineteenth and early twentieth centuries,
the mercantile system served the interests of merchants and producers
such as the British East India Company, whose activities were protected
or encouraged by the state.

 Absolute Advantage
Smith’s Views on Mercantilism
Smith made a number of important criticisms of mercantilist
doctrine. First, he demonstrated that trade, when freely initiated,
benefits both parties. In modern jargon it is a positive-sum game.
Second, he argued that specialization in production allows for
economies of scale, which improves efficiency and growth. Finally,
Smith argued that the collusive relationship between government
and industry was harmful to the general population. While the
mercantilist policies were designed to benefit the government and
the commercial class, the doctrines of laissez-faire, or free markets,
which originated with Smith, interpreted economic welfare in a far
wider sense of encompassing the entire population.

 Absolute Advantage
Main Content of Absolute Advantage
When one nation is more efficient than another in the production of one
commodity but is less efficient than the other nation in producing a second
commodity, then both nations can gain by each specializing in the
production of the commodity of its absolute advantage and exchanging
part of its output with the other nation for the commodity of its absolute
disadvantage. By this process, resources are utilized in the most efficient
way and the output of both commodities will rise. This increase in the
output of both commodities measures the gains from specialization in
production available to be divided between the two nations through free
trade. (page 33)
Trade only happens under the mutually beneficial gains ,otherwise, no
trade.
 Illustration of Absolute Advantage

No Trade
Wheat (bushels/man-hour)
Cloth (yards/man-hour)
 With Trade
U.S.
6
4
U.K.
1
5
U.S.
12
0
U.K.
0
10
Wheat (bushels/man-hour)
Cloth (yards/man-hour)
 After Trade
Output wheat increases 5 units(12-7,before trade)
Output cloth increases 1 unit (10-9, before trade);
The world output increases 5 units wheat and 1 unit cloth.
U.S. gains 2 units wheat while U.K. gains 4 units cloth.
 Main Views on Trade
Under the heavy pressure of high smuggling and created variety of
products during the industrial revolution, by 1860 England had
removed the last vestiges of the mercantile era .
Adam Smith's insight that free trade leads to international specialization
of labor and, usually, to greater economic well-being for all nations.
What do nations trade? (two-win games)
What the gains from trade? ( the greater economic well-being)
What is the pattern of trade? (import and export)
(supposing with two nations, two products and one factor “labor” world.
One nation should export the more efficient product and import the less
efficient product compared with the other nation. In other words, the
nation should export the less cost product and import the higher cost
product)
 Comments
Further development of mercantilism
1. The world’s economic pie is not a fixed quantity
2. Mutually beneficial game

Only applying to a small number of countries
E.G. Developed countries to developing countries

Shortcomings
1. 2×2×1 theory model is not enough
2. The cost advantage of trade reason is too absolute
How to explain the trade happened among the developed countries and
among the developing countries?
How to explain a country without any cost advantage also trade with
other countries?
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 Conclusion
The Principle of Absolute Advantage (Cost Advantage)
In a two-nation, two-product world, international trade and
specialization will be beneficial when one nation has an absolute cost
advantage (that is, uses less labor to produce a unit of output) in one good
and the other nation has an absolute cost advantage in the other good. A
nation will import those goods in which it has an absolute cost advantage;
and it will export those goods in which it has an absolute cost advantage.

Mutually beneficial game
Each nation benefits by specializing in the production of the good that it
produces at a lower cost than the other nation, while importing the good
that it produces at a higher cost.

Increase of the world’s output
More efficient used resources as the result of specializing to increase the
world’ output , which is distributed to the two nations through trade.

Comparison of Mercantilism and Absolute
Advantage
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Mercantilism-zero sum game-one nation
gains at the expense of the other
Adam Smith-both nations can gain from
trade
Absolute Advantage-each nation should
specialize in production of good which is
the most efficient at producing
2.4 Trade Based on Comparative
Advantage: David Ricardo
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The Law of Comparative Advantage
The Gains from Trade
Exception to the Law of Comparative
Advantage
Comparative Advantage with Money
Comments
Conclusion
 The Law of Comparative Advantage

Introduction

Countries engage in international trade for two basic
reasons:
•
•
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•
They are different from each other in terms of climate,
land, capital, labor, and technology.
They try to achieve scale economies in production.
The Ricardian model is based on technological differences
across countries.
These technological differences are reflected in
differences in the productivity of labor.

 The Law of Comparative Advantage
David Recardo (1772-1823)
David Ricardo was one of those rare people who
achieved tremendous success and lasting fame.
After his family disinherited him for marrying outside
his Jewish faith, Ricardo made a fortune as a
stockbroker and a loan broker. When he died, his
estate was worth over $100 million in today's dollars.
At age twenty-seven, after reading Adam Smith's The Wealth of Nations,
Ricardo got excited about economics. He wrote his first economics
article at age thirty-seven and then spent only fourteen years—his last
ones—as a professional economist. His Principles of Political Economy
and Taxation was published in 1817, in which he presented the law of
comparative advantage, one of the most important and still unchallenged
laws of economics, with many practical applications.
Ricardo first gained notice among economists over the "bullion
controversy." In 1809 he wrote that England's inflation was the
result of the Bank of England's propensity to issue excess bank
notes. In short, Ricardo was an early believer in the quantity theory
of money, or what is known today as monetarism.
In his Essay on the Influence of a Low Price of Corn on the Profits of
Stock (1815), Ricardo articulated what came to be known as the law of
diminishing returns. One of the most famous laws of economics, it holds
that as more and more resources are combined in production with a
fixed resource—for example, as more labor and machinery are used on
a fixed amount of land—the additions to output will diminish.
Ricardo also opposed the protectionist Corn Laws(谷物法), which
restricted imports of wheat. In arguing for free trade, Ricardo formulated
the idea of comparative costs, today called comparative advantage
(LTV: Labor Theory of Value). Comparative advantage—a very subtle
idea—is the main basis for most economists' belief in free trade today.
The idea is this: a country that trades for products that it can get at lower
cost from another country is better off than if it had made the products at
home.

 The Law of Comparative Advantage
The Concept of Law of Comparative Advantage
In a two-nation and two-commodity world economy, even if one nation
is less efficient than the other nation in the production of both
commodities, there is still a basis for mutually beneficial trade. The first
nation should specialize in the production of and export the commodity in
which its absolute disadvantage is smaller (the commodity of its
comparative advantage) and import the commodity in which its absolute
disadvantage is greater (the commodity of its comparative disadvantage).
Note that in a two-nation, two-commodity world, once it is determined
that one nation has a comparative advantage in one commodity, then the
other nation must necessarily have a comparative advantage in the other
commodity.
 The Law of Comparative Advantage

•
•
•
•
•
•
•
Assumptions of the model:
Only two countries and two commodities in the world (Home and
Foreign)
Free Trade
Perfect mobility of labor within each nation but immobility
between the two nations
Constant costs of production
No transportation cost
No technical change
The labor theory of value
 The Law of Comparative Advantage
The Illustration of Comparative Advantage
Without Trade
U.S.
U.K.
Wheat (bushels/man-hour)
6
1
Cloth (yards/man-hour)
4
2

Explanation: US has an absolute advantage of both wheat and
cloth with respect to UK, but the absolute advantage is greater in
wheat(6:1) than cloth (4:2), US has a comparative advantage in
wheat. On the contrary , UK’s comparative advantage in cloth
( smaller absolute disadvantage).
 The Gains from Trade
If the trade exchange rate is equal to the domestic exchange
rate , no trade happens. Only trading partners can gains by
each specializing in the production and exporting the
commodity of its comparative advantage, international trade
happens.
E.G. (page table 2.2)
With Trade (specialization)
U.S.
U.K.
Wheat (bushels/man-hour)
12
0
Cloth (yards/man-hour)
0
4
Explanation: If US exports 6w for 4c from UK, and UK exports 2c
for 1w from US, no trade happens since it is the same with
domestic exchange without trade .
If US exports 6w for the exchange of 6c (more than 4c) from UK,
US gains 2c ( or save one-half hour work). While UK exports 6c for
the exchange of 6w , UK can gains 6c ( 6w=12c in UK, 6c for 6w,
6c surplus).
Trade can happen between 4c ﹤ 6w ﹤12c ( it is measured in
terms of cloth, and also can measured in terms of wheat).
The spread between 12c and 4c represents the total gains from
trade available to be shared by the two nations by trading 6w.
The closer the rate of exchange is to 4c=6w, the smaller is the
share of the gain going to the US and the larger going to UK, and
verse versa
 Exception to the Law of Comparative
Advantage

When the absolute disadvantage that one nation has with
respect to another nation is the same in both commodities.
E.G. see table 2.2
If UK produces wheat 3w per hour not 1w, no mutually beneficial
Trade between US and UK.

The modification of the law of comparative advantage
Even if one nation has an absolute disadvantage with respect to
the other nation in the production of both commodities, there is still a
basis for mutually beneficial trade, unless the absolute disadvantage
( that one nation has with respect to the other nation) is in the same
proportion for the two commodities.
 Comparative Advantage with Money
The comparative advantage can be expressed in terms of
currency of either nation (Price difference)
E.G. See table 2.2
U.S.
U.K.
Wheat (bushels/man-hour)
6 ($1)
1($2)
Cloth (yards/man-hour)
4 ($1.5)
2 ($1)
Suppose that the wage rate in US is $6 dollar per hour, since one
man-hour produces 6w in US, the price of a bushel of wheat is Pw
= $1, Pc=$1.5; Suppose UK 1pound per hour, Pw=1pound,
Pc=0.5pound. If the exchange rate 1pound =$2, Pw=$2, Pc=$1
Business people would buy the lower price of wheat in US and sell them
in UK; on the contrary buying the lower price of cloth in UK and sell
them in US.

 Comparative Advantage with Money
The exchange rate influences the international trade
E.G. If 1 pound = $1, in UK Pw=$1 and Pc=$0.5
No trade happens in Wheat from US to UK, and UK would
export more cloth to US. Trade would be unbalanced in favor of the
UK, and the exchange rate between the dollar and the pound would
have to rise.
E.G. If 1 pound =$3, in UK Pw=$3 and Pc=$1.5( the same with US)
No trade happens in Cloth from UK to US, and US would export
more wheat to UK. Trade surplus in UK would decrease while US
trade deficit would decrease, and imbalance trade between the two
countries would decrease.
Therefore , each country need pay attention to its own currency
exchange rate to other nation’s.

 Comparative Advantage with Money
Against One Argument in US
The argument that could be advanced in the United States that it needs
to protect the high wages and standard of living of its workers against
cheap labor is generally false. At the same time, the protection of the
labor against more efficient labor is also false.
Reasons: high wages means high cost of products, less competition of
products. Protection of less efficient labor means less efficiency in
production, resulting high cost of products, less competition.

 Comments
The law of comparative advantage coined the absolute
advantage , and absolute advantage can be view as the
special situation of comparative advantage .

On foreign trade, Ricardo set forth his famous theory of
comparative advantage.
Ricardo's argument was that there are gains from trade if each
nation specializes completely in the production of the good in
which it has a "comparative" cost advantage in producing, and
then trades with the other nation for the other good.

Ricardo took economics to an unprecedented degree of
theoretical sophistication. He formalized the Classical
system more clearly and consistently than anyone
before had done

 Comments
Theory of value
Three periods of time
1. The first began with his acquaintance with systematic economic
writing and extended through the bullion controversy, and might
be described as a consistent exposition of Adam Smith's
original concept of value.
2. The second phase of Ricardo's treatment of value is directly
traceable to the corn-law controversies of 1813-17 .
3. Ricardo's Principles of Political Economy and Taxation was
published in the spring of 1817, but more fundamentally to

vindicate "embodied labour" as the soundest theoretical
and the best practical measure of value.
 Conclusion

We examined the Ricardian model, the simplest model
that shows how differences between countries give rise
to trade and gains from trade.

In this model, labor is the only factor of production and
countries differ only in the productivity of labor in
different industries.

In the Ricardian model, a country will export that
commodity in which it has comparative (as opposed to
absolute) labor productivity advantage.
 Conclusion


The fact that trade benefits a country can be
shown in either of two ways:
• We can think of trade as an indirect method of
production.
• We can show that trade enlarges a country’s
consumption possibilities.
The distribution of the gains from trade
depends on the relative prices of the goods
countries produce.
 Conclusion

Extending the one-factor, two-good model to a
world of many commodities makes it possible
to illustrate that transportation costs can give
rise to the existence of nontraded goods.

The basic prediction of the Ricardian modelthat countries will tend to export goods in
which they have relatively high productivityhas been confirmed by a number of studies.
2.5 Comparative Advantage and
Opportunity Costs






Comparative Advantage and the Labor
Theory of Value
The Opportunity Cost Theory
The Production Possibility Frontier
under Constant Costs
Opportunity Costs and Relative
Commodity Prices
Comments
Conclusion
 Comparative Advantage and the
Labor Theory of Value
One-Factor Theory
With comparative advantage, only the factor of labor is used to measure
the cost of the produced commodity, then a nation exports the lower cost
commodity and import the higher cost commodity compared with its
trading partner. In other words, the comparative advantage is explained by
the labor theory of value. It
means:
1. Labor is the only factor of production and used in the same fixed
proportion in the production of all commodities (constant cost);
2. Labor is homogeneous

Unreality in the Real World
Labor not only one factor of production ( capital, land….); different
produced commodities having different proportion inputs of factor; labor
not homogeneous ( training, productivity, wages)

 The Opportunity Cost Theory

Introduction
the Marginalist Revolution of 1871-74 represented the beginning
of Neoclassical Economic Theories. It attacked the one-factor theory
( comparative advantage with the explanation of labor theory of value).
It was Gottfried von Haberler(1900- )in 1936 that he explained the
theory of comparative advantage on the opportunity cost theory. In this
form, the law of comparative advantage is sometimes referred to as
the law of comparative cost.
 The Opportunity Cost Theory
The Representative and Works
Haberler's two major works - Theory of
International Trade (1936) and Prosperity and
Depression (1937) – were hailed as masterly
tomes(学术或理论巨著) which, for the first time in
either field, drew together numerous scattered
ideas into a single theoretical treatment which
was both encyclopaedic(百科全书的或广博的)
and rigorous(严密的). His rewriting of the theory of
comparative advantage in terms of opportunity cost, rather than real
cost, led to a long debate with Jacob Viner

 The Opportunity Cost Theory
Concept of Opportunity Cost Theory
It means the cost of commodity is the amount of a second commodity
that must be given up to release just enough resources to produce one
additional unit of the first commodity. Consequently, the nation with the
lower opportunity cost in the production of a commodity has a
comparative advantage in that commodity ( and a comparative
disadvantage in the second commodity) .
(No assumption one production factor of labor and of homogeneous; no
assumption the price or cost of production depending on the labor
content exclusively.)
E.G. Table 2.2 If in the absence of trade, US must give up two-thirds of
a unit of cloth to release just enough to produce one additional unit of
wheat domestically, then the opportunity cost of wheat is two-thirds of a
unit of cloth, while 2 in UK, so US’s comparative advantage in wheat.

 The Opportunity Cost Theory

Conclusion
According to the law of comparative advantage, US should specialize in
producing wheat and export some of it in exchange for British cloth. This
is exactly what we conclude earlier with the law of comparative
Advantage based on the labor theory of value, but now the explanation
is based on the opportunity cost theory.
How to show or illustrate the opportunity costs?
Answer: production possibility frontier (PPF) or transformation curve
 The Production Possibility Frontier
under Constant Costs

Production Possibility Frontier
It is a curve that shows the alternative combinations of the two
commodities that a nation can produce by fully utilizing all of its
resources with the best technology available to it.
See table 2.4 (page 42) to show:
1. US’s opportunity cost of wheat is two-thirds of a unit of cloth, while
the opportunity cost of cloth is one and one-second units of wheat;
2. UK’s opportunity cost of wheat is two units of cloth, while the
opportunity cost of cloth is one-second of a unit of wheat;
 The Production Possibility Frontier
under Constant Costs

Illustration of PPF
FIGURE 2-1 The Production Possibility Frontiers of the United States and
the United Kingdom.
 The Production Possibility Frontier
under Constant Costs
Explanation of PPF
1. Points inside or below, the PPF is also possible but is inefficient, in
the sense that the nation has some idle resources and / or is not
using the best technology available to it; On the other hand, points
above the PPF cannot be achieved with the resources and
technology currently available to the nation.
2. The downward, or negative, slope of the PPF

It indicates that one nation wants to produce one commodity more ,
another production of commodity must be given up some.
3. The straight line of PPF
It means the opportunity costs are constant .
 The Production Possibility Frontier
under Constant Costs
Constant Opportunity Costs
It happens :
1. Resources or factors of production are either perfect substitutes for
each other or used in fixed proportion in the production of both
commodities.
2. All units of the same factor are homogeneous or of exactly the same
quality.
Conclusion: the constant opportunity costs differ among nations,
providing the basis for trade.
But constant costs are not realistic, They are discussed only because
they serve as a convenient introduction to the more realistic case of
increasing costs, discussed in the next chapter.

 Opportunity Costs and Relative
Commodity Prices
The opportunity cost of a commodity is given by the (absolute)
slope (vertical / horizontal ) of the production possibility frontier,
or transformation curve, and is sometimes referred to as the
marginal rate of transformation (MRT).
E.G. Figure 2.1 (page 44) shows that the (absolute of slope of US
transformation curve is 120/180=2/3= opportunity cost of wheat
in US and remain constant; while UK is 120/60=2=opportunity
cost of wheat in UK and remains constant.
If suppose the prices equal costs of production and the nation
produces both some wheat and some cloth, the opportunity cost of
wheat is equal to the price of wheat relative to the price cloth (Pw/Pc).
Thus in US Pw/Pc=2/3 and Pc/Pw=1.5, while in UK Pw/Pc=2 and
Pc/Pw=1/2.

FIGURE 2-1 The Production Possibility Frontiers of the United States
and the United Kingdom.
 Opportunity Costs and Relative
Commodity Prices
Conclusion: The lower Pw/Pc in US means the comparative
advantage in the production of wheat, and verse versa.
The lower Pc/Pw=1/2 in UK means the comparative
advantage in the production of cloth.

The difference in relative commodity prices between the two
nations (given by the difference in the slope of their
transformation curves) is a reflection of their comparative
advantage and provides the basis for mutually beneficial trade.
 Comments

Opportunity cost theory further explains the
basis for mutually beneficial trade from
marginalism .

The assumption of the constant opportunity
cost is unrealistic.

The constant cost is exclusively decided by
production, or supply. Demand consideration
do not enter in the determination of relative
commodity prices.
 Conclusion

To explain the basis for mutually beneficial trade
Labor theory of value (David Ricardo) →Opportunity
cost theory (marginalism) → (absolute) slope of
the production possibility frontier (Transformation
Curve)→ the relative price of the commodity (price
difference)→ trade basis

Opportunity cost of a commodity is equal to the relative
price of that commodity and is given by the (absolute)
slope of the production possibility frontier.
2.6 The Basis for and the Gains
from Trade Under Constant Costs




Illustration of the Gains from Trade
Relative Commodity Prices with Trade
Comments
Conclusion
 Illustration of the Gains from Trade

Without Trade ( production possibility frontier also
represents its consumption frontier

With trade, how the two nations gain from trade (figure 2-2)
FIGURE 2-2 The Gains from Trade.

Explanation of Figure 2-2
1. Without trade, A represents the combination (90w and 60c) of
US ; A’ represents the combination (40w and 40c) of UK.
2. With trade, US specializes in the production of wheat according
to comparative advantage theory; UK specializes in the
production of cloth .
3. US by exchanging 70w for 70c with UK, US ends up consuming
at E ( gains 20w and 10c); while UK by exchanging 70c for 70w
with US, UK ends up consuming at E’ (30w and 10c).

Conclusion
The increased consumption of both wheat and cloth in both
nations was made possible by the increased output (50w and 20c)
at resulted as each nation specialized in the production of the
commodity of its comparative advantage.
 Relative Commodity Prices with Trade

Another Figure(2-3 page 46) shows relative commodity
prices with trade
FIGURE 2-3 Equilibrium-Relative Commodity Prices with Demand and Supply.
Explanation
How the equilibrium-relative commodity price with
specialization in production and trade is determined?
1. Left panel E is the equilibrium-relative commodity price with
production of wheat and trade is determined. Pw/Pc=1. It
means that the equilibrium quantity of 180w is produced in US.
2. Right panel E’ is the equilibrium –relative commodity price with
production of cloth and trade is determined. Pc/Pw=1. It means
that the equilibrium quantity of 120cloth is produced in UK.
3. With trade, wheat is only produced in US and US specializes
completely in the production of wheat; while cloth is only
produced in UK and UK specializes completely in the
production of cloth.

 Comments
With trade each country can specialize in the
production of its comparative advantage
completely and benefit from the international trade .
I n r e a l i t y, i t i s i m p o s s i b l e , w h i l e p a r t i a l
specialization is common.
 Conclusion
In the absence of trade, a nation’s production possibility
frontier is also its consumption frontier. With trade, each
nation can specialize in producing the commodity of its
comparative advantage and exchange part of its output with
the other nation for the commodity of its comparative
disadvantage. By so doing, both nations end up consuming
more of both commodities than without trade. With complete
specialization, the equilibrium-relative commodity prices will
be between the pretrade-relative commodity prices prevailing
in each nation.
2.7 Empirical Tests of the
Ricardian Model
Examination of empirical tests of Ricardo Model
If we allow for different labor productivities in various industries in
different nations, Ricardo trade model does a reasonably good job at
explaining the patter of trade.
1. Mac Dougall in 1951 and 1952 using labor productivity and
export data for 25 industries in US and UK for the year 1937

Relative Labor Productivities and Comparative Advantage–United
States and United Kingdom.
Conclusion: Positive relationship between labor productivity and
exports, higher productivity more exports.
(see figure 2-4)
FIGURE 2-4
2.7 Empirical Tests of the
Ricardian Model
2. Golub study in 1995
The conclusion is that in general , relative unit labor costs( the ratio of
wages to unit labor productivity) and exports were inversely related.
That is to say, the lower labor costs more exports, and verse versa.
The color line shows a clear negative correlation between relative unit
labor costs and relative exports for the 33 industries . Supporting
Ricardo model.
(See figure 2-5)
FIGURE 2-5 Relative Exports and Relative Unit Costs– United States
and Japan.
Chapter Summary


This chapter examined the development of trade theory
from the mercantilism to Smith, Ricardo, and Haberler and
sought to answer three basic questions: (1) what is the
basis for trade? (2) What are the gains from trade? (3) what
is the pattern of trade?
Although Ricardo theory was confirmed by many empirical
studies, the model explains neither the reason for the
difference in labor productivity or costs across nations nor
the effect of international trade on the earnings of factors.
Exercises
Additional Reading:
1. Comments on Mercantilism
2. Free Trade & Trade Protection Arguments
Exercises
Discussion Questions:
1. Explain the contribution of mercantilism to economic
theory
2. Explain the contribution of classical free trade theories to
economic theory
3. Explain the main argument on free trade
Internet Materials
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http://www.iie.org
http://www.wto.org
http://www.oecd.org
http://www.citizen.org/trade/index.cfm
http://www.un.org/depts/unsd/mbsreg.htm