Markets with Within-Type Adverse Selection
研究一个卖方拥有多单位商品（每单位有高低两种质量）且私下知道自己的“类型”（即劣质品数量）及哪些是劣质品时的双边贸易，刻画了信息约束下帕累托最优的分配集，并给出了帕累托改进的条件。
We study bilateral trade with a seller owning multiple units of a good, where each unit is of binary quality. The seller privately knows her “type”—defined by the number of lemons that she owns—and which units in her endowments are the lemons (“ within-type adverse selection”). We characterize the set of informationally constrained Pareto optimal allocations and show that every such allocation must involve a trade characterized by a threshold λ ∗ , with types having less (more) than λ ∗ units of lemons selling only their lemons (selling their entire endowment). We provide conditions for a distribution shift that give Pareto-improving allocations.