Specialization and Human Capital
证明，人力资本利用的规模报酬递增为专业化、贸易和通过投资创造比较优势提供了激励，即使生产技术是规模报酬不变的，相同禀赋的个人也有动机进行技能投资专业化并相互贸易。
Incentives for specialization, trade, and the production of comparative advantage through investment are shown to arise from increasing returns to utilization of human capital. Indivisibilities imply fixed-cost elements of investment that are independent of subsequent utilization. Hence the rate of return is increasing in utilization and is maximized by utilizing specialized skills as intensively as possible. Identically endowed individuals have incentives to specialize their investments in skills and trade with each other for this reason, even if production technology exhibits constant returns to scale.