International Trade and Economic Growth: A Diagrammatic Analysis
用简单的几何图形分析标准的两国两部门两要素贸易模型，展示如何通过资本劳动比和相对价格实现稳态均衡，适合想避开复杂数学的读者。
As others have noted (see articles by Harry Johnson (1971, 1972) and Jaroslav Vanek), the highly mathematical nature of most of the literature integrating growth and trade theory serves to restrict considerably the size of the audience to which explanations of this important subject can be directed.' This paper attempts to widen this audience by framing the analysis of the topic in simple geometric terms that utilize the standard two-country, two-sector (commodity), two-factor model of international trade. Assume that the two commodities produced by the two countries A and B are a capital good K and a consumption good C. The capital good together with a growing labor force L are the two factors of production.2 As is typical for this model, also suppose that the capital good cannot be traded once it is used as a productive factor and that this good is produced in a uniformly laborintensive fashion compared to the consumption good.3 The production function of each good is identical in both countries and subject to constant returns to scale.4 It is further assumed that the growth rate of the labor force is the same in both countries and that each economy saves a constant but different proportion of its income.5 There are two requirements for steadystate equilibrium in such a model: 1) The desired rate of capital accumulation in both countries must equal the exogenously determined rate of growth of the labor force, and 2) The value of exports must equal the value of imports for each of the two countries.6 As the first step in the analysis, it will be shown that over some range of capital-labor (K/L) endowment ratios for each country, there is for each of these endowment ratios some relative price of the capital good in terms of the consumption good (Pk) that will equalize the desired rate of capital accumulation in each country and the common rate of labor force growth. After finding the set of Pk and K/L ratios for each country satisfving this equilibrium condition, the next step will be to select the subset of Pk at which the two countries wish to trade in opposite directions, and determine for each of these Pk the relative size of the countries as measured bv the ratio of their labor supplies that would be needed to equalize the value of exports and imports in each country. Given some actual initial ratio of the size of the two labor forces a ratio that remains constant throughout the growth process, since the rates of labor force growth are equal in the two countries it will then be possible to read off from this schedule of * Professor of economics, University of Wisconsin, Madison. ' The exposition of these authors deals mainly with the case of a small country facing fixed terms of trade whereas the analysis here focuses on the more general case where there are two countries, each of which can affect the terms of trade. 2 For simplicity, depreciation of the capital good is ignored. Some initial supply of K and L in each country is also assumed. 3This assumption concerning factor intensity is made to insure a unique, stable steady-state equilibrium. I Such other standard assumptions of the simple Heckscher-Ohlin-Samuelson model as diminishing marginal productivity and perfect competition are also made. I In each economy, all individuals have the same savings ratio and possess the same quantity of capital. 6 When the desired rate of capital accumulation in a country equals the labor force growth rate, the country's supply of the capital good will generally not equal its demand for this good. However, the trading condition required for equilibrium insures that one country's excess demand for K is matched by the other country's excess supply. Thus, the two requirements can be combined into the more familiar condition that the actutal rate of capital accumulation equal the common growth rate of the labor force.