DOES NEUTRAL STABILITY IMPLY LYAPUNOV STABILITY

A central concept in evolutionary game theory is that of an evolutionarily stable strategy. However, many games of interest for economics have only strategies which meet the weaker requirement of neutral stability. While neutral stability implies Lyapunov stability under the replicator dynamics in pairwise interactions, we give here an example in which an evolutionarily stable strategy is not Lyapunov stable in a more general context. We propose to use instead the notions of (strong) uninvadability and (strong) unbeatability, refinements of evolutionary and neutral stability, respectively. Strong uninvadability implies asymptotic stability, and strong unbeatability implies Lyapunov stability under the replicator dynamics. (C) 1995 Academic Press, Inc.