假定一个劳动充裕的国家和一个土地充裕的国家都使用同样的技术生产劳动密集型和土地密集型的产

品。参照第4章的分析方法，首先分析两国问贸易使劳动力流动动因减少的条件;然后，使用第5章中的分析方法说明一国征收关税能够产生劳动力流动的动因。

Suppose that a labor-abundant country and a land-abundant country both produce labor- and land-intensive goods with the same technology. Drawing on the analysis in Chapter 4， first analyze the conditions under which trade between the two countries eliminates the incentive for labor to migrate. Then， using the analysis in Chaptes 5， show that a tariff by one country will create an incentive for labor migration.