Collusion in Auctions with Externalities
研究买家之间存在外部性时拍卖中的合谋行为，发现外部性会导致合谋不完美，卖家可通过设计拍卖实现对买家群体事后无效率的合谋结果，并刻画了买家事前激励有效的合谋机制。
In standard auctions, collusion among buyers eliminates bidding competition despite informational asymmetries. Collusion can, however, be imperfect when the situation involves externalities among buyers, that is, when a buyer is worse off if one rival wins the goon rather than if nobody gets it. For intermediate values of the externality and under various objective functions, the seller finds it optimal to design an auction that leads, in equilibrium, to a collusive outcome that is ex post inefficient for the group of buyers; an ex ante incentive-efficient collusion mechanism for the buyers is characterized in this situation.