The Emergence of Local Norms in Networks

We develop an explanation of the emergence of local norms, and theassociated phenomenon of geographical variation in behavior.Individuals are assumed to interact locally with neighbors in anenvironment with a network externality. Although many patterns ofbehavior are possible, the dispersed interactive choices of agentsare shown to select behavior that is locally uniform but globallydiverse. The range of applications of the theory includes regionalvariation in the practice of medicine, technology choice, andcorruption. The framework is also useful for further developing ourunderstanding of important phenomena like lock-in, criticalthresholds, and contagion.