North-South Asymmetry in Returns to Scale, Uneven Development, and the Population Puzzle

本研究建立了一个南北贸易与经济发展的模型。该模型符合两个经验事实：(1)各国人均收入增长率不同；(2)发达国家和发展中国家的人口增长与人均收入增长之间的关系不同。我们假设，北方和南方分别具有规模收益递增和规模收益递减的技术特征。由于贸易条件的影响，在平衡增长道路上，两国的实际国民收入以相同的速度增长。然而，由于人口增长的差异，实际人均收入以不同的速度增长。在发达国家，人口增长与人均收入增长之间的相关性可以是正的，也可以是负的，而在发展中国家，这种相关性是负的。

This research develops a model of North-South trade and economic development. The model is consistent with two empirical facts : (1) the growth rate of income per capita differs across countries ; and (2) the relationship between the growth of population and that of income per capita differs for developed and developing countries. We assume that the North and the South are characterized by increasing-returns-to-scale and decreasing-returns-to-scale technologies, respectively. Real national income grows at the same rate in both countries along the balanced growth path owing to a terms of trade effect. However, real income per capita grows at different rates because of population growth differentials. In developed countries, the correlation between population growth and income {\it per capita} growth can be positive or negative while in developing countries, the correlation is negative.