Chapter 3 特定要素模型（Specific Factors and Income Distribution） • 导论（Introduction） • 特定要素模型（The Specific Factors Model） • 特定要素模型中国际贸易（International Trade in the Specific Factors Model） • 收入分配与贸易得益（Income Distribution and the Gains from Trade） • 贸易的政治经济学（The Political Economy of Trade: A Preliminary View） • 总结（Summary） • 附录（Appendix: Further Details on Specific Factors）
Introduction导论 • Trade has substantial effects on the income distribution within each trading nation.不同国家之间的贸易对收入分配产生较大的影响 • There are two main reasons why international trade has strong effects on the distribution of income:两个主要原因 • Resources cannot move immediately or costlessly from one industry to another.资源不能无成本和快速地从一个行业转向另外一个行业。 • Industries differ in the factors of production they demand。行业对生产要素的需要不同 • The specific factors model allows trade to affect income distribution.特定要素模型考虑了贸易对收入分配的影响。
3-1 The Specific Factors Model • Assumptions of the Model（模型假设） • Assume that we are dealing with one economy that can produce two goods, manufactures and food.（一个国家能生产两种商品：制造品和粮食） • There are three factors of production; labor (L), capital (K) and land (T for terrain).（三种生产要素） • Manufactures are produced using capital and labor (but not land).（生产制造品只使用劳动力和资本，不需要土地） • Food is produced using land and labor (but not capital). • Labor is therefore a mobile factor that can be used in either sector.（粮食生产只需要劳动力和土地，劳动力可以在两个生产部门流动） • Land and capital are both spe‘cific factors that can be used only in the production of one good.（土地和资本是特定要素） • Perfect Competition prevails in all markets.（完全竞争）
How much of each good does the economy produce?一个经济体不同商品各生产多少 • The economy’s output of manufactures depends on how much capital and labor are used in that sector.生产多少依赖于要素投入的多少 • This relationship is summarized by a production function.产出与投入之间的关系可由生产函数来概括。 • Theproduction function for good X gives the maximum quantities of good X that a firm can produce with various amounts of factor inputs.商品X的生产函数是不同要素投入所能生产出商品X的最大数量。 • For instance, the production function for manufactures (food) tells us the quantity of manufactures (food) that can be produced given any input of labor and capital (land).
制造品的生产函数The production function for manufactures is given by QM = QM (K, LM) (3-1) where: • QM is the economy’s output of manufactures制造品产出 • K is the economy’s capital stock资本存量 • LMis the labor force employed in manufactures制造行业中劳动力的使用量 • 粮食生产函数The production function for food is given by QF = QF (T, LF) (3-2) where: • QF is the economy’s output of food粮食产出 • T is the economy’s supply of land土地供应量 • LF is the labor force employed in food粮食生产使用的劳动量
约束条件The full employment of labor condition requires that the economy-wide supply of labor must equal the labor employed in food plus the labor employed in manufactures:充分就业要求两部门使用的劳动力与总劳动力供应相等 LM + LF = L(3-3) • We can use these equations and derive the production possibilities frontier of the economy.我们可以根据这些等式推导出生产可能性边界
Production Possibilities生产可能性边界 • To analyze the economy’s production possibilities, we need only to ask how the economy’s mix of output changes as labor is shifted from one sector to the other.为了分析经济体的生产可能性，我们需要知道当劳动力从一个部门移向另外一个部门时产出组合将如何变化。 • Figure 3-1 illustrates the production function for manufactures.
Figure 3-1: The Production Function for Manufactures 制造业的生产可能性边界 Output产出, QM QM = QM(K, LM) Labor input劳动投入, LM
递减的边际收益The shape of the production function reflects the law of diminishing marginal returns.生产函数的形状反映了递减的边际收益 • Adding one worker to the production process (without increasing the amount of capital) means that each worker has less capital to work with.增加一个劳动进行生产意味着每个工人将占用更少的资本 • Therefore, each additional unit of labor will add less to the production of output than the last.因此，将导致产出增量减少 • Figure 3-2 shows the marginal product of labor, which is the increase in output that corresponds to an extra unit of labor.
Figure 3-2: The Marginal Product of Labor Marginal product of labor, MPLM MPLM Labor input, LM
Figure 3-3: The Production Possibility Frontier in the Specific Factors Model 粮食产量Output of food, QF (increasing ) 1' 2' QF =QF(K, LF) Q2F 3' L2F PP 制造品产量Output of manufactures, QM (increasing ) 粮食生产投入的劳动Labor input in food, LF(increasing ) L Q2M L2M 1 2 3 L AA 制造品投入的劳动量Labor input in manufactures, LM (increasing ) QM =QM(K, LM) 生产可能性边界Economy’s production possibility frontier (PP) Production function for food粮食生产函数 制造品生产函数Production function for manufactures 劳动力配置Economy’s allocation of labor (AA)
价格，工资与劳动配置（Prices, Wages, and Labor Allocation） • 各个部门将投入多少劳动？（How much labor will be employed in each sector?） • 要问答这个问题必须了解劳动力市场的供求（To answer the above question we need to look at supply and demand in the labor market.） • 劳动需求Demand for labor: • 在每个部门，作为利润最大化的雇主，将使雇佣的劳动国数量处于当增加一个劳动者所带来的利润等于工资支出的位置。In each sector, profit-maximizing employers will demand labor up to the point where the value produced by an additional person-hour equals the cost of employing that hour.
制造部门劳动力需求曲线可以表达为:(The demand curve for labor in the manufacturing sector can be written:) MPLM x PM = w (3-4) • 即制造部门的工资等于劳动边际产品的价值（The wage equals the value of the marginal product of labor in manufacturing.） • The demand curve for labor in the food sector can be written: MPLF x PF = w (3-5) • The wage rate equals the value of the marginal product of labor in food.
The wage rate must be the same in both sectors, because of the assumption that labor is freely mobile between sectors.（由于劳动力是自由流动的，所以两个生产部门工资率必须相等） • The wage rate is determined by the requirement that total labor demand equal total labor supply: LM + LF = L (3-6)
Figure 3-4: The Allocation of Labor Wage rate, W Wage rate, W PFX MPLF (Demand curve for labor in food) 1 W1 PMX MPLM (Demand curve for labor in manufacturing) Labor used in manufactures, LM Labor used in food, LF L1M L1F 总劳动力供应Total labor supply, L
At the production point the production possibility frontier must be tangent to a line whose slope is minus the price of manufactures divided by that of food.（在生产点上，生产可能性边界一定和一条斜率等于负的制造品价格除以粮食价格的直线相切） • Relationship between relative prices and output: -MPLF/MPLM = -PM/PF (3-7)
Output of food, QF 1 Q1F PP Output of manufactures, QM Q1M Figure 3-5: Production in the Specific Factors Model （社会在生产可能性边界上斜率负的制造品相对价格的点上进行生产） Slope = -(PM/PF)1
What happens to the allocation of labor and the distribution of income when the prices of food and manufactures change?（当两种产品价格发生变化时，劳动力和收入如何变化？） • Two cases: • An equal proportional change in prices（价格同比例变化） • A change in relative prices（相对价格变化）
Figure 3-6: An Equal Proportional Increase in the Prices of Manufactures and Food 同比例变化的情况 PF2 X MPLF Wage rate, W PM2X MPLM Wage rate, W PM1 X MPLM 2 W2 PF1 X MPLF 1 W1 Labor used in manufactures, LM Labor used in food, LF PM increases 10% PF increases 10% 10% wage increase
When both prices change in the same proportion, no real changes occur. • The wage rate (w) rises in the same proportion as the prices, so real wages (i.e. the ratios of the wage rate to the prices of goods) are unaffected. • The real incomes of capital owners and landowners also remain the same. • 没有真实变化，变化只是名义工资和名义价格，真实收入和劳动力雇佣数没有任何变化。
When only PM rises, labor shifts from the food sector to the manufacturing sector and the output of manufactures rises while that of food falls.当只有PM 升高时，劳动力从粮食部门转移到制造品部门，制造品部门产出提高，而粮食部门产出减少。 • The wage rate (w) does not rise as much as PMsince manufacturing employment increases and thus the marginal product of labor in that sector falls.工资率没有价格升高那么多，原因是：劳动边际收益递减。
Figure 3-7: A Rise in the Price of Manufactures 制造业部门价格上升 Wage rate, W Wage rate, W PF1X MPLF 2 Wage rate rises by less than 7% W 2 1 PM2X MPLM W1 PM1X MPLM Labor used in manufactures, LM Labor used in food, LF Amount of labor shifted from food to manufactures 7% upward shift in labor demand
Figure 3-8: The Response of Output to a Change in the Relative Price of Manufactures 制造品相对价格变化引起总产出变化 Output of food, QF Q1F 1 Q2F 2 PP Q2M Output of manufactures, QM Q1M Slope = - (PM/PF)1 Slope = - (PM /PF) 2
Figure 3-9: Determination of Relative Prices Relative price 相对价格 of manufactures, PM/PF RS 1 (PM /PF)1 RD Relative quantity相对数量 of manufactures, QM/QF (QM /QF)1
相对价格与收入分配Relative Prices and the Distribution of Income • Suppose that PM increases by 10%. Then, we would expect the wage to rise by less than 10%, say by 5%. • What is the economic effect of this price increase on the incomes of the following three groups?相对价格变化对不同得益集团收入的经济影响是如何的呢？ • Workers工人 • Owners of capital资本所有者 • Owners of land土地所有者
Workers: • We cannot say whether workers are better or worse off; this depends on the relative importance of manufactures and food in workers’ consumption.取决于工人的消费偏好，即制造品和粮食在他们消费中所占比例更多。 • Owners of capital: • They are definitely better off.以制造品衡量的实际工资率下降。即资本所有者收益上升大于价格上升幅度。 • Landowners: • They are definitely worse off.以粮食衡量的实际工资率上升；制造品的价格上升。
3-2 International Trade in the Specific Factors Model特定要素模型中的国际贸易 • Assumptions of the model • Assume that both countries (Japan and America) have the same relative demand curve.在给定的相对价格下，相对需求民相等（相同的相对需求曲线）） • Therefore, the only source of international trade is the differences in relative supply. The relative supply might differ because the countries could differ in:相对供应不同：国际贸易的唯一来源 • Technology • Factors of production (capital, land, labor)
资源与相对供应（Resources and Relative Supply） • What are the effects of an increase in the supply of capital stock on the outputs of manufactures and food?当资本存量的供应增加时，对制造品和粮食产出的影响是什么呢？ • A country with a lot of capital and not much land will tend to produce a high ratio of manufactures to food at any given prices.价格一定时，拥有大量资本和少量土地的国家将生产更多 的制造品和少量的粮食。
Wage rate, W Wage rate, W PF1 X MPLF 2 W2 1 W1 PMX MPLM2 PMX MPLM1 Amount of labor shifted from food to manufactures Labor used in food, LF Labor used in manufactures, LM Figure 3-10: Changing the Capital Stock 假如日本资本存量增加，其影响如何呢？ Increase in capital stock, K
An increase in the supply of capital would shift the relative supply curve to the right.（资本增加使制造部门相对供应曲线右移） • An increase in the supply of land would shift the relative supply curve to the left.（土地增加使制造部门相对供应曲线左移） • What about the effect of an increase in the labor force? （劳动力增加的效应又如何呢？） • The effect on relative output is ambiguous, although both outputs increase.两部门产出均增加，所以结论是模糊的、不确定的。
Trade and Relative Prices贸易和相对价格 • Suppose that Japan has more capital per worker than America, while America has more land per worker than Japan.假定 • As a result, the pretrade relative price of manufactures in Japan is lower than the pretrade relative price in America. • International trade leads to a convergence of relative prices.国际贸易导致相对价格趋同。
Figure 3-11: Trade and Relative Prices Relative price of manufactures, PM /PF RSA RSWORLD (PM/PF )A RSJ (PM /PF )W (PM/PF)J RDWORLD Relative quantity of manufactures, QM/QF
The Pattern of Trade贸易模式 • In a country that cannot trade, the output of a good must equal its consumption. 封闭经济下，产出等于消费。 • DM=QM DF=QF • International trade makes it possible for the mix of manufactures and food consumed to differ from the mix produced. 贸易使得一个国家可以消费不同于产出的组合。 • A country cannot spend more than it earns. 消费不能超过收入。 • PM*DM+PF*DF=PM*QM +PF*QF
Figure 3-12: The Budget Constraint for a Trading Economy 参与贸易国的预算约束 Consumption of food, DF Output of food, QF 1 Q1F Production possibility curve Consumption of manufactures, DM Output of manufactures, QM Q1M Budget constraint (slope = -PM/PF)
Figure 3-13: Trading Equilibrium Quantity of food Quantity of food America’s food exports Japan’s food imports Quantity of manufactures Quantity of manufactures QJM QAM DJM DAM Japan’s manufactures exports America’s manufactures imports American budget constraint Japanese budget constraint QAF DAF DJF QJF
3-3 Income Distribution and the Gains from Trade收入分配与贸易得益 • To assess the effects of trade on particular groups, the key point is that international trade shifts the relative price of manufactures and food. • Trade benefits the factor that is specific to the export sector of each country, but hurts the factor that is specific to the import-competing sectors.Trade has ambiguous effects on mobile factors. • 结论：贸易使出口部门特定要素所有者受益，使进口产品竞争部门特定要素的所有者受损，而对流动要素所有者的影响具有不确定性。
Could those who gain from trade compensate those who lose, and still be better off themselves?贸易收益是否一定大于贸易损失呢？ • If so, then trade is potentially a source of gain to everyone. • The fundamental reason why trade potentially benefits a country is that it expands the economy’s choices.贸易对一国具有潜在收益的基本原因是增加该经济体的消费选择。 • This expansion of choice means that it is always possible to redistribute income in such a way that everyone gains from trade.
Figure 3-14: Trade Expands the Economy’s Consumption Possibilities Consumption of food, DF Output of food, QF 2 1 Budget constraint (slope = - PM/PF) Q1F PP Q1M Consumption of manufactures, DM Output of manufactures, QM
3-4 The Political Economy of Trade: A Preliminary View • Trade often produces losers as well as winners. • Optimal Trade Policy • The government must somehow weigh one person’s gain against another person’s loss. • Some groups need special treatment because they are already relatively poor (e.g., shoe and garment workers in the United States). • Most economists remain strongly in favor of more or less free trade. • Any realistic understanding of how trade policy is determined must look at the actual motivations of policy.
Income Distribution and Trade Politics • Those who gain from trade are a much less concentrated, informed, and organized group than those who lose. • Example: Consumers and producers in the U.S. sugar industry
Summary • International trade often has strong effects on the distribution of income within countries, so that it often produces losers as well as winners. • Income distribution effects arise for two reasons: • Factors of production cannot move instantaneously and costlessly from one industry to another. • Changes in an economy’s output mix have differential effects on the demand for different factors of production.
Summary • A useful model of income distribution effects of international trade is the specific-factors model. • In this model, differences in resources can cause countries to have different relative supply curves, and thus cause international trade. • In the specific factors model, factors specific to export sectors in each country gain from trade, while factors specific to import-competing sectors lose. • Mobile factors that can work in either sector may either gain or lose.
Summary • Trade nonetheless produces overall gains in the sense that those who gain could in principle compensate those who lose while still remaining better off than before.
Marginal Product of Labor, MPLM MPLM dLM Labor input, LM Appendix:Further Details on Specific Factors Figure 3A-1: Showing that Output Is Equal to the Area Under the Marginal Product Curve
Marginal Product of Labor, MPLM Income of capitalists MPLM Labor input, LM Appendix:Further Details on Specific Factors Figure 3A-2: The Distribution of Income Within the Manufacturing Sector w/PM Wages
Marginal Product of Labor, MPLM Increase in capitalists’ income MPLM Labor input, LM Appendix:Further Details on Specific Factors Figure 3A-3: A Rise in PM Benefits the Owners of Capital (w/PM)1 (w/PM)2
Marginal Product of Labor, MPLF Decline in landowners’ income MPLF Labor input, LF Appendix:Further Details on Specific Factors Figure 3A-4: A Rise in PM Hurts Landowners (w/PF)2 (w/PF)1
Reading • 杨小凯、张永生（2001）：新贸易理论、比较利益理论及其经验研究的新成果：文献综述，《经济学（季刊）》10月，第1卷第1期 • 程祖伟(2004):正确解读萨缪尔森- 琼斯的特定要素贸易理论，《经济经纬》第3期
Question • P61,3