The Emergence of Local Norms in Networks

We develop an explanation of the emergence of local norms, and the associated phenom- enon of geographical variation in behavior. Individuals are assumed to interact locally with neighbors in an environment with a network externality. Although many patterns of behavior are possible, the dispersed interactive choices of agents are shown to select behavior that is locally uniform but globally diverse. The range of applications of the theory includes regional variation in the practice of medicine, technology choice, and corruption. The framework is also useful for further developing our understanding of important phenomena like lock-in, critical thresholds, and contagion