Equilibrium and Optimality in a Mean-Variance Model
重新审视对称均值-方差世界中市场配置最优性的旧争论，考虑生产非凸性、不完全相关产出和自由进入，发现瓦尔拉斯均衡不存在，并比较了两种非瓦尔拉斯均衡的资源配置效率。
This article reexamines an old debate over the optimality of market allocations in a symmetric mean-variance world, with production nonconvexities, imperfectly correlated outputs, and free entry. We show that Walrasian equilibrium does not exist: that non-Walrasian equilibrium under price-taking behavior allocates resources optimally between the risky and risk-free sectors, but spreads resources in the risky sector over an insufficient number of activities; and that non-Walrasian equilibrium under consistent conjectures allocates insufficient resources to the risky sector, and spreads them over an excessive number of activities. These results have analogues in the theory of product differentiation.