22 November 2005. Eric Rasmusen,
[email protected]. Http://www.rasmusen.org. 6 Dynamic Games with Incomplete Information 6.1 Perfect Bayesian Equilibrium: Entry Deterrence II and III Asymmetric information, and, in particular, incomplete information, is enormously impor- tant in game theory. This is particularly true for dynamic games, since when the players have several moves in sequence, their earlier moves may convey private information that is relevant to the decisions of players moving later on. Revealing and concealing information are the basis of much of strategic behavior and are especially useful as ways of explaining actions that would be irrational in a nonstrategic world. Chapter 4 showed that even if there is symmetric information in a dynamic game, Nash equilibrium may need to be refined using subgame perfectness if the modeller is to make sensible predictions. Asymmetric information requires a somewhat different refine- ment to capture the idea of sunk costs and credible threats, and Section 6.1 sets out the standard refinement of perfect bayesian equilibrium. Section 6.2 shows that even this may not be enough refinement to guarantee uniqueness and discusses further refinements based on out-of- equilibrium beliefs. Section 6.3 uses the idea to show that a player’s ignorance may work to his advantage, and to explain how even when all players know something, lack of common knowledge still affects the game. Section 6.4 introduces incomplete information into the repeated prisoner’s dilemma and shows the Gang of Four solution to the Chain- store Paradox of Chapter 5. Section 6.5 describes the celebrated Axelrod tournament, an experimental approach to the same paradox.