Voluntarily Separable Repeated Prisoner's Dilemma
构建了一个玩家可单方面结束关系并随机匹配新对手的重复囚徒困境模型，发现内生关系时长会显著改变演化稳定结构，多态均衡比单态均衡更早出现合作者、效率更高。
Ordinary repeated games do not apply to real societies where one can cheat and escape from partners. We formulate a model of endogenous relationships that a player can unilaterally end and start with a randomly assigned new partner with no information flow. Focusing on two-person, two-action Prisoner's Dilemma, we show that the endogenous duration of partnerships generates a significantly different evolutionary stability structure from ordinary random matching games. "Monomorphic" equilibria require initial trust building, while a "polymorphic" equilibrium includes earlier cooperators than any strategy in monomorphic equilibria and is thus more efficient. This is due to the non-linearity of average payoffs. Copyright Copyright © 2009 The Review of Economic Studies Limited.