Equilibria and optima generally differ in imperfectly competitive markets. While this is well understood theoretically, it is unclear how large the welfare distortions are in the aggregate economy. Do they matter quantitatively? To answer this question, we develop a multi-sector monopolistic competition model with endogenous firm entry and selection, productivity, and markups. Using French and British data, we quantify the gap between the equilibrium and optimal allocations. In our preferred specification, inefficiencies in the labor allocation and entry between sectors, as well as inefficient selection and output per firm within sectors, generate welfare losses of about 6–10% of GDP.

中文翻译：

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量化垄断竞争下的均衡与最佳差距*

不完全竞争市场中的均衡和最优通常有所不同。尽管从理论上可以很好地理解这一点，但尚不清楚总体经济中的福利扭曲有多大。它们在数量上重要吗？为了回答这个问题，我们开发了具有内生企业进入和选择，生产率和加价的多部门垄断竞争模型。使用法国和英国的数据，我们可以量化均衡分配与最优分配之间的差距。在我们的首选规范中，部门之间劳力分配和进入效率低下，部门内部每家公司的选择和产出效率低下，会产生约占GDP的6-10％的福利损失。