2005/05 | LEM Working Paper Series | |
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A Note on Equilibrium Selection in Polya-Urn Coordination Games |
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Giorgio Fagiolo |
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Keywords | ||
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Coordination Games, Equilibrium Selection, Pareto-Efficient vs. Risk-
Dominant Equilibrium, Polya-Urn Schemes.
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JEL Classifications | ||
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C72, C73.
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Abstract | ||
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We study equilibrium selection in coordination games played by a population whose
size increases over time. In each time period, a new player enters the economy,
observes current strategy shares and irreversibly chooses a strategy on the basis of
expected payoffs. We employ a simple Polya-Urn scheme to discuss the efficiency of
long-run equilibria under alternative individual decision rules (e.g. best-reply, logit,
etc.). We show that the system delivers a predictable outcome only when agents
employ either a linear or a logit probability rule. If agents employ deterministic
best-reply rules, Pareto-efficient coordination can occur, but the actual outcome depends
on initial conditions and chance. In all other cases, coexistence of strategies
characterizes equilibrium configurations.
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