Robust Predictions in Infinite-Horizon Games--an Unrefinable Folk Theorem
证明了在无限期博弈中，任何贝叶斯纳什均衡策略在微小扰动下仍为唯一理性化策略，并推导出不可精炼的民间定理：任何个体理性且可行的收益都是某扰动类型下的唯一理性化收益向量。
We show that in any game that is continuous at infinity, if a plan of action a i is played by a type t i in a Bayesian Nash equilibrium, then there are perturbations of t i for which a i is the only rationalizable plan and whose unique rationalizable belief regarding the play of the game is arbitrarily close to the equilibrium belief of t i . As an application to repeated games, we prove an unrefinable folk theorem: any individually rational and feasible payoff is the unique rationalizable payoff vector for some perturbed type profile. This is true even if perturbed types are restricted to believe that the repeated-game payoff structure and the discount factor are common knowledge. Copyright , Oxford University Press.