中文摘要
市场规模扩大（例如源于全球化）如何影响福利？我们使用一个包含垄断竞争、异质性加成率和固定成本的模型研究这一问题。我们刻画了福利的变化，并将配置效率的变化分解为三种效应：（1）由于竞争加剧，在价格弹性异质的企业之间发生的再配置；（2）由于边际盈利企业退出而发生的再配置；（3）由于企业加成率变化而发生的再配置。第二和第三种效应对福利的影响并不明确，而第一种效应——我们称之为达尔文效应——无论需求曲线形状如何，总是提高福利。我们用比利时制造业企业的数据对需求曲线进行非参数校准，并对结果进行量化。我们发现，微观层面轻微的规模报酬递增可以催化宏观层面大幅度的规模报酬递增。规模报酬递增中有 70% 至 90% 来自更大市场在资源配置方式上的改善。这些收益的绝大部分源于达尔文效应，它提高了总体加成率，并将销售和就业集中于高加成率企业。这对政策具有启示意义：进入补贴借助达尔文式再配置，即使进入多于最优水平，也能改善福利。
Abstract
Abstract How does an increase in market size, say due to globalization, affect welfare? We study this question using a model with monopolistic competition, heterogeneous markups, and fixed costs. We characterize changes in welfare and decompose changes in allocative efficiency into three different effects: (1) reallocations across firms with heterogeneous price elasticities due to intensifying competition, (2) reallocations due to the exit of marginally profitable firms, and (3) reallocations due to changes in firms’ markups. Whereas the second and third effects have ambiguous implications for welfare, the first effect, which we call the Darwinian effect, always increases welfare regardless of the shape of demand curves. We nonparametrically calibrate demand curves with data from Belgian manufacturing firms and quantify our results. We find that mild increasing returns at the microlevel can catalyze large increasing returns at the macrolevel. Between 70 and 90% of increasing returns to scale come from improvements in how a larger market allocates resources. The lion’s share of these gains are due to the Darwinian effect, which increases the aggregate markup and concentrates sales and employment in high-markup firms. This has implications for policy: an entry subsidy, which harnesses Darwinian reallocations, can improve welfare even when there is more entry than in the first best.