Competitive Profits in the Long Run
构建了一个动态完全竞争模型，证明考虑沉没成本对进入和退出的影响后，即使竞争性行业的长期平均利润率也存在差异。
Profit rates differ across industries. Explanations have often relied on static models of imperfect competition. This paper develops a dynamic model of perfect competition to demonstrate that long-run average profit rates differ even across competitive industries when the effects of sunk costs on entry and exit are considered. The hypothesis that firms maximize their present expected values has few empirical implications for long-run average profit rates, but it does have implications for the behaviour of variables over time; for example, industries with high variability in the number of firms should exhibit low variability in firm values.