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第二章劳动生产率和比较优势：李嘉图模型
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导论
比较优势的概念
单一要素经济
单一要素经济中的贸易
对比较优势的误解
多商品中的比较优势
运输费用和非贸易品
对李嘉图模型的实证研究
总结
1
导论
• 国家之间进行国际贸易基于两个基本的
原因：
– 一是差异：气候、资源、技术等
– 二是生产中的规模经济 scale economies(规模
经济)
• 李嘉图模型（The Ricardian model ）基于各
国间技术差异
– 技术差异反映在劳动生产率上
（ productivity of labor）.
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2-1 比较优势的概念
• 美国情人节的例子。On Valentine’s Day the
U.S. demand for roses is about 10 million
（100万支） roses.
• 美国在冬天种植玫瑰比较困难：
– 加热的温室
– 其投入的资源是比较多的（能源、劳动力、资
本）
• 这些资源也可以用来生产其他商品，如计
算机.
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• Opportunity Cost（机会成本）
– The opportunity cost of roses （A) in terms of computers （B) is the number of
computers（B) that could be produced with the same resources as a given
number of roses（A).
– 以商品B衡量生产商品A的机会成本，就是生产一定数量商品A所消耗的资
源所能生产商品B的数量。
– 例：生产1000万支玫瑰的机会成本是10万台计算机；而生产10万计算机的
机会成本是1000万支玫瑰。
更为准确地说，生产一支玫瑰的机会成本是？台计算机；而生产一台计算
机的机会成本是？支玫瑰。
• Comparative Advantage（比较优势）
– A country has a comparative advantage in producing a good if the opportunity
cost of producing that good in terms of other goods is lower in that country than
it is in other countries.
– 如果一国生产一种产品的机会成本（用其他商品衡量）低于其他国家生产
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该种产品的机会成本，则该国在生产此种产品上具有比较优势。
• 假定美国生产100支玫瑰的资源可以用来
生产10万台计算机。
• 假定在南美生产100支玫瑰的资源可以用
来生产3万台计算机.
• 这就假定南美比美国的劳动生产率更低。
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• 如果每个美国均专业化生产机会成本更
低的商品，则贸易使双方受益。
• 在南美玫瑰的机会成本更低，而美国计
算机的机会成本更低。
• 从贸易中获利可以从双方计算机和玫瑰
产量的变化得到。
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Table 2-1: 产量的变化
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玫瑰的机会成本 计算机的机会成
本
United States
0.01
100
South America
0.003
333
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• The example in Table 2-1 illustrates the principle of
comparative advantage:
– If each country exports the goods in which it has comparative
advantage (lower opportunity costs), then all countries can in
principle gain from trade.
• What determines comparative advantage?
– Answering this question would help us understand how
country differences determine the pattern of trade (which
goods a country exports). （Ricardian Model）
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2-2 A One-Factor Economy
• Assume that we are dealing with an economy (which
we call Home). In this economy（五个假定条件）
– Labor is the only factor of production.（一种要素:劳动
力）
– Only two goods (say wine and cheese) are produced.（两
种商品）
– The supply of labor is fixed in each country.（劳动要素
供应不变）
– The productivity of labor in each good is fixed.（劳动生
产率不变）
– Perfect competition prevails in all markets.（完全竞争）
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• The constant labor productivity is modeled with the
specification of unit labor requirements:
– The unit labor requirement （单位产品劳动投入）is the
number of hours of labor required to produce one unit of
output.（单位：人小时，person-hours）
• Denote with aLW the unit labor requirement for wine (e.g. if aLW = 2,
then one needs 2 hours of labor to produce one gallon of wine).
• Denote with aLC the unit labor requirement for cheese (e.g. if aLC = 1,
then one needs 1 hour of labor to produce a pound of cheese).
• 总资源为劳动力（L）The economy’s total resources
are defined as L, the total labor supply (e.g. if L = 120,
then this economy is endowed with 120 hours of labor
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or 120 workers).
• Production Possibilities(生产能力)
– The production possibility frontier (PPF，生产可能性边
界) of an economy shows the maximum amount of a good
(say wine) that can be produced for any given amount of
another (say cheese), and vice versa.（生产可能性边界：给
定一种产品产量时，能够生产另外一种产品的最大可能
产量）
– The PPF of our economy is given by the following equation:
(2-1)
aLC×QC + aLW×QW ≤L
– From our previous example, we get:
QC + 2QW ≤ 120
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Figure 2-1: Home’s Production Possibility Frontier
Home wine
production, QW,
in gallons
L/aLW
P
Absolute value of slope equals
opportunity cost of cheese in
terms of wine
F
L/aLC Home cheese
production, QC,
in pounds
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• Relative Prices and Supply
– The particular amounts of each good produced are
determined by prices.
– The relative price (相对价格)of good X (cheese) in
terms of good Y (wine) is the amount of good Y (wine)
that can be exchanged for one unit of good X (cheese).
– Examples of relative prices:
• If a price of a can of Coke is $0.5, then the relative price of
Coke is the amount of $ that can be exchanged for one unit of
Coke, which is 0.5.
• The relative price of a $ in terms of Coke is 2 cans of Coke per
dollar.
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• Denote with PC the dollar price of cheese and with PW
the dollar price of wine. Denote with wW the dollar wage
in the wine industry and with wC the dollar wage in the
cheese industry.(工资率)：葡萄酒部门工资率为PW /
aW
• Then under perfect competition, the non-negative profit
condition implies:
– If PW / aW < wW, then there is no production of QW.
– If PW / aW = wW, then there is production of QW.
– If PC / aC < wC, then there is no production of QC.
– If PC / aC = wC, then there is production of QC.
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• The above relations imply that if the relative price of
cheese (PC / PW ) exceeds its opportunity cost (aLC / aLW),
then the economy will specialize in the production of
cheese.（当奶酪的相对价格大于其机会成本时，该国
才会专业化生产奶酪）
• In the absence of trade, both goods are produced, and
therefore PC / PW = aLC /aLW.
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2-3 Trade in a One-Factor World
• Assumptions of the model（模型假设）:
– 1.There are two countries in the world (Home and Foreign).
– 2.Each of the two countries produces two goods (say wine
and cheese).
– 3.Labor is the only factor of production(生产要素).
– 4.The supply of labor is fixed in each country.
– 5.The productivity of labor in each good is fixed.
– 6.Labor is not mobile across the two countries.
– 7.Perfect competition prevails in all markets.
– 8.All variables with an asterisk re’fer to the Foreign country.
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• Absolute Advantage(绝对优势)
– A country has an absolute advantage in a production of a
good if it has a lower unit labor requirement than the
foreign country in this good.
– 即，当一个国家能以少于其他国家的劳动投入生产出
同样单位商品时，则该国在生产此商品上具有绝对优
势。
– Assume that aLC < a*LC and aLW < a*LW
• This assumption implies that Home has an absolute advantage in
the production of both goods. Another way to see this is to notice
that Home is more productive in the production of both goods than
Foreign.
• Even if Home has an absolute advantage in both goods, beneficial
trade is possible.
• The pattern of trade will be determined by the
concept of comparative advantage.
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• Comparative Advantage
– 假设本国用酒衡量的奶酪的机会成本小于外国
（Assume that aLC /aLW < a*LC /a*LW）
(2-2)
• This assumption implies that the opportunity cost of cheese in
terms of wine is lower in Home than it is in Foreign.
• Home has a comparative advantage in cheese and will
export it to Foreign in exchange for wine.
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图 2-2: 外国的生产只要能性曲线
外国葡萄酒的产量 Q*W,
in gallons
L*/a*LW
F*
+1
P*
L*/a*LC
外国奶酪的产量, Q*C ,
in pounds
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• Determining the Relative Price After Trade
– What determines the relative price (e.g., PC / PW)
after trade?
• To answer this question we have to define the relative
supply and relative demand for cheese in the world as a
whole.
• The relative supply of cheese equals the total quantity
of cheese supplied by both countries at each given
relative price divided by the total quantity of wine
supplied, (QC + Q*C )/(QW + Q*W).
• The relative demand of cheese in the world is a
similar concept.
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Figure 2-3: World Relative Supply and Demand
Relative price
of cheese, PC/PW
a*LC/a*LW
RS
1
aLC/aLW
RD
2
RD'
Q'
L/aLC
L*/a*LW
Relative quantity
of cheese, QC + Q*C
QW + Q*W
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• The Gains from Trade
– If countries specialize according to their
comparative advantage, they all gain from this
specialization and trade.
– We will demonstrate these gains from trade in
two ways.
– First, we can think of trade as a new way of
producing goods and services (that is, a new
technology).
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– Another way to see the gains from trade is to
consider how trade affects the consumption in
each of the two countries.
– The consumption possibility frontier states the
maximum amount of consumption of a good a
country can obtain for any given amount of the
other commodity.
– In the absence of trade, the consumption
possibility curve is the same as the production
possibility curve.
– Trade enlarges the consumption possibility for
each of the two countries.
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Figure 2-4: Trade Expands Consumption Possibilities
消费可能的扩张
Quantity
of wine, Q*W
Quantity
of wine, QW
F*
T
P
F
Quantity
of cheese, QC
(a) Home
T*
P*
Quantity
of cheese, Q*C
(b) Foreign
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 A Numerical Example
• The following table describes the technology of
the two counties:
Table 2-2: Unit Labor Requirements
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• The previous numerical example implies that:
aLC / aLW = 1/2 < a*LC / a*LW = 2
– In world equilibrium, the relative price of cheese must lie
between these values. Assume that Pc/PW = 1 gallon of
wine per pound of cheese.
• Both countries will specialize and gain from this
specialization.
– Consider Home, which can transform wine to cheese by
either producing it internally or by producing cheese and
then trading the cheese for wine.
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– Home can use one hour of labor to produce
1/aLW = 1/2 gallon of wine if it does not trade.
– Alternatively, it can use one hour of labor to
produce 1/aLC = 1 pound of cheese, sell this
amount to Foreign, and obtain 1 gallon of wine.
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– In the absence of trade, Foreign can use one
unit of labor to produce 1/a*LC = 1/6 pound of
cheese using the domestic technology.
– Can it do better by specializing in wine and
trading wine with Home for cheese?
– In the presence of trade, Foreign can use one
unit of labor to produce 1/a*LW = 1/3 gallon of
wine.
– Since the world price of wine is PW / PC = 1
pound of cheese per gallon, Foreign can obtain
1/3 lb of cheese which is more than 1/6 lb.
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• ’Relative Wages(相对工资)
– Because there are technological differences
between the two countries, trade in goods does
not make the wages equal across the two
countries.
– A country with absolute advantage in both
goods will enjoy a higher wage after trade.
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– This can be illustrated with the help of a numerical
example:
• Assume that PC = $12 and that PW = $12. Therefore, we have
PC / PW = 1 as in our previous example.
• Since Home specializes in cheese after trade, its wage will be
(1/aLC)PC = ( 1/1)$12 = $12.
• Since Foreign specializes in wine after trade, its wage will be
(1/a*LW) PW = (1/3)$12 = $4.
• Therefore the relative wage of Home will be $12/$4 = 3.
• Thus, the country with the higher absolute advantage will
enjoy a higher wage after trade.
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2-4 Misconceptions About Comparative
Advantage
• Productivity and Competition
– Myth 1: Free trade is beneficial only if a country is
strong enough to withstand foreign competition.
• This argument fails to recognize that trade is based on
comparative not absolute advantage.
• The Pauper Labor Argument
– Myth 2: Foreign competition is unfair and hurts
other countries when it is based on low wages.
• Again in our example Foreign has lower wages but still
benefits from trade.
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• Exploitation
– Myth 3: Trade makes the workers worse off in
countries with lower wages.
• In the absence of trade these workers would be worse
off.
• Denying the opportunity to export is to condemn poor
people to continue to be poor.
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Table 2-3: Changes in Wages and Unit Labor Costs
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2-5 Comparative Advantage with
Many Goods
多产品模型中的比较优势
• 模型建立（Setting Up the Model）
– Both countries consume and are able to produce a large
number, N, of different goods.
按两国生产产品的相对劳动投入排序：
a*L1/aL1 ＜a*L2/aL2 ＜ a*L3/aL3 ＜…＜ a*LN/aLN
• 相对工资与专业化（Relative Wages and
Specialization）
– 贸易模式依赖于两国的劳动工资（The pattern of trade
will depend on the ratio of Home to Foreign wages.）
– 成本最低原则选择产品进行专业化生产Goods will
always be produced where it is cheapest to make them.
• For example, it will be cheaper to produce good i in Home if
• waLi < w*a*Li
• a*Li/aLi > w/w*.
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Table 2-4: Home and Foreign Unit Labor Requirements
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• 哪个国家生产哪些产品Which country
produces which goods?
– A country has a cost advantage in any good for
which its relative productivity is higher than its
relative wage.（取决于相对工资率和相对生
产效率）
• If, for example, w/w* = 3, Home will produce apples,
bananas, and caviar, while Foreign will produce
only dates and enchiladas.
• Both countries will gain from this specialization.
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• Determining the Relative Wage in the Multigood
Model（多产品模型中相对工资的决定）
– To determine relative wages in a multigood economy
we must look behind the relative demand for goods (i.e.,
the relative derived demand).（通过相对劳动需求与
供给来决定－对劳动力的相对需求是根据对能生产
产品推算出来的派生需求）
– The relative demand for Home labor depends
negatively on the ratio of Home to Foreign wages.（当
本国对外国的相对工资率上升时，对本国劳动的相
对派生需求将减少。两个原因：一是本国生产产品
价格更高，二是本国能生产的产品种类减少）
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Figure 2-5: Determination of Relative Wages
Relative wage
Rate, w/w*
RS
Apples
10
8
4
3
2
0.75
Bananas
Caviar
Dates
Enchiladas
RD
Relative quantity
of labor, L/L*
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2-6 运输费用和非贸易品Adding Transport Costs
and Nontraded Goods
• 国际经济中，专业分工不是极端的原因有三个（There are
three main reasons why specialization in the real international
economy is not extreme）:
– 1、多种要素The existence of more than one factor of production.
– 2、贸易保护Countries sometimes protect industries from foreign
competition.
– 3、运输费用和非贸易品It is costly to transport goods and services.
• The result of introducing transport costs makes some goods
nontraded.
• In some cases transportation is virtually impossible.
– Example: Services such as haircuts and auto repair cannot be traded
internationally.
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1975年
Developed
countries
America
Canada
Australia
Japan
France
Germany
Britain
Switzerland
1.065
1.066
1.027
1.070
1.132
1.049
1.041
1.072
1.026
1985年
1.048
1.047
1.025
1. 118
1.082
1.039
1.028
1.045
1.010
1995年
1.044
1.037
1.027
1.067
1.090
1.034
1.028
1.025
1.010
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1975年
Developing
Countries
1.128
Africa
1.120
Asia
1.097
Middle East
1.136
western hemisphere 1.111
FIF＝（CIF）/（FOB）
1985年
1.
1.
1.
1.
1.
118
126
088
105
091
1995年
1.
1.
1.
1.
1.
114
120
087
097
090
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2-7 Empirical Evidence on the
Ricardian Model
Figure 2-6: Productivity and Exports
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• MacDougall(1951）
• Balassa(1963）
• Stephen S.Golub(1995)
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• .
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• .
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Reading
• 邵润堂、张华（1999）：比较优势、竞争优势
及国际竞争力，《经济问题》第4期
• 洪银兴（1997）：从比较优势到竞争优势——
兼论国际贸易的比较利益理论的缺陷，《经济
研究》第6期
• 符正平（1999）：比较优势与竞争优势的比较
分析——兼论新竞争经济学及其启示，《国际
贸易问题》第8期
48
Question
作业：P35, 3，5
思考：1、石油价格由劳动价值决定吗？
2、中东产油国的财富来自国民的勤
劳还是上帝的恩施？
3、如何评价美国经济增长中知识贡
献已占42%。
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