Theoretical Economics 3 (2008), 155–192 1555-7561/20080155 Monotone methods for equilibrium selection under perfect foresight dynamics Daisuke Oyama Graduate School of Economics, Hitotsubashi University Satoru Takahashi Department of Economics, Princeton University Josef Hofbauer Department of Mathematics, University of Vienna This paper studies a dynamic adjustment process in a large society of forward- looking agents where payoffs are given by a supermodular normal form game. The stationary states of the dynamics correspond to the Nash equilibria of the stage game. It is shown that if the stage game has a monotone potential maximizer, then the corresponding stationary state is uniquely linearly absorbing and glob- ally accessible for any small degree of friction. A simple example of a unanimity game with three players is provided where there are multiple globally accessible states for a small friction. Keywords. Equilibrium selection, perfect foresight dynamics, supermodular game, strategic complementarity, stochastic dominance, potential, monotone potential. JEL classification. C72, C73. 1. Introduction Supermodular games capture the key concept of strategic complementarity in various economic phenomena. Examples include oligopolistic competition, the adoption of new technologies, bank runs, currency crises, and economic development. Strategic complementarity plays an important role in particular in Keynesian macroeconomics Daisuke Oyama:
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[email protected] This paper has been presented at the Universities of Tokyo, Vienna, and Wisconsin–Madison, and con- ferences/workshops in Heidelberg, Kyoto, Marseille, Prague, Salamanca, San Diego, Tokyo, Urbino, and Vienna. We are grateful to the audiences as well as to Drew Fudenberg, Michihiro Kandori, Akihiko Mat- sui, Stephen Morris, William H.