It is well known that the rock-paper-scissors game has no pure saddle point. Weshow that this holds more generally: A symmetric two-player zero-sum game hasa pure saddle point if and only if it is not a generalized rock-paper-scissors game.Moreover, we show that every finite symmetric...

We show that for many classes of symmetric two-player games, the simple decision rule \imitate-the-best" can hardly be beaten by any other decision rule. Weprovide necessary and sufficient conditions for imitation to be unbeatable and showthat it can only be beaten by much in games that are of...

Sick-pay is a common provision in labor contracts. It insures workersagainst a sudden loss of income due to unexpected absences andhelps them smooth consumption. Therefore, many governments findsick-pay socially desirable and choose to mandate its provision. Butsick-pay is not without its...

We show that for many classes of symmetric two-player games, the simple decision rule "imitate-the-best" can hardly be beaten by any other decision rule. We provide necessary and sufficient conditions for imitation to be unbeatable and show that it can only be beaten by much in games that are of...

We show that for many classes of symmetric two-player games, the simple decision rule "imitate-the-best" can hardly be beaten by any other decision rule. We provide necessary and sufficient conditions for imitation to be unbeatable and show that it can only be beaten by much in games that are of...

We show that in symmetric two-player exact potential games, the simple decision rule "imitate-if-better" cannot be beaten by any strategy in a repeated game by more than the maximal payoff difference of the one-period game. Our results apply to many interesting games including examples like 2x2...

We characterize the class of symmetric two-player games in which tit-for-tat cannot be beaten even by very sophisticated opponents in a repeated game. It turns out to be the class of exact potential games. More generally, there is a class of simple imitation rules that includes tit-for-tat but...