VERTICAL PRODUCT DIFFERENTIATION AND NORTH-SOUTH TRADE
研究北方和南方之间的国际贸易，北方出口高质量产品，南方出口低质量产品。南方人口增长或技术进步会改变各国出口产品结构，并导致产品周期：北方放弃最低质量产品，由南方生产。
The authors study international trade between the North and the South where the industrial sector produces goods of different quality. The North exports high-quality products, the South low-quality products. Faster population growth in the South changes the spectrum of products exported by every country, and so does faster technical progress in the southern industrial sector. The latter leads also to the introduction of new high-quality products and the abandonment of old low-quality products. In all cases, there is a product cycle; the North abandons the production of its lowest-quality products which are subsequently produced in the South. Copyright 1987 by American Economic Association.