Evolution and Walrasian Behavior in Market Games

We revisit the question of price formation in general equilibrium theory. We explore whether evolutionary forces lead to Walrasian equilibrium in the context of a market game, introduced by Shubik (1972). Market games have Pareto inferior (strict) Nash equilibria, in which some, and possibly all, markets are closed. We introduce a strong version of evolutionary stable strategies (SESS) for finite populations. Our concept requires stability against multiple, simultaneous mutations. We show that the introduction of a small number of “trading mutants” is sufficient for Pareto improving trade to be generated. Provided that agents lack market power, Nash equilibria corresponding to approximate Walrasian equilibria constitute the only approximate SESS.