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This paper reexamines the paradoxical aspect of the electronic mail game (Rubinstein, 1989). The electronic mail game is a coordination game with payoff uncertainty. At a Bayesian Nash equilibrium of the game, players cannot achieve the desired coordination of actions even when a high order of mutual knowledge of payoff functions obtains. We want to make explicit the role of knowledge about rationality of players, not only that of payoff functions. For this purpose, we use an extended version of the belief system model developed by Aumann and Brandenburger (1995). We propose a certain way of embedding the electronic mail game in an belief system. And we show that for rational players to coordinate their actions, for any embedding belief systems, it is necessary that the upper bound order of mutual knowledge of payoff functions exceeds the upper bound order of mutual knowledge of rationality. This result implies that under common knowledge of rationality, the coordination never occurs, which is similar to Rubinstein's result. We point out, however, that there exists a class embedding belief systems for which the above condition is also sufficient for the desired coordination.

This paper studies the incentive compatibility of solutions to generalized indivisible good allocation problems introduced by Sönmez (1999), which contain the well-known marriage problems (Gale and Shapley, 1962) and the housing markets (Shapley and Scarf, 1974) as special cases. In particular, I consider the vulnerability to manipulation of solutions that are individually rational and Pareto optimal. By the results of Sönmez (1999) and Takamiya (2003), any individually rational and Pareto optimal solution is strategy-proof if and only if the strong core correspondence is essentially single-valued, and the solution is a strong core selection. Given this fact, this paper examines the equilibrium outcomes of the preference revelation games when the strong core correspondence is not necessarily essentially single-valued. I show that for the preference revelation games induced by any solution which is individually rational and Pareto optimal, the set of strict strong Nash equilibrium outcomes coincides with the strong core. This generalizes one of the results by Shin and Suh (1996) obtained in the context of the marriage probelms. Further, I examine the other preceding results proved for the marriage problems (Alcalde, 1996; Shin and Suh, 1996; Sönmez, 1997) to find that none of those results are generalized to the general model.