The Evolution of Social Norms

Social norms are patterns of behavior that are self-enforcing within a group: Everyone conforms, everyone is expected to conform, and everyone wants to conform when they expect everyone else to conform. Social norms are often sustained by multiple mechanisms, including a desire to coordinate, fear of being sanctioned, signaling membership in a group, or simply following the lead of others. This article shows how stochastic evolutionary game theory can be used to study the resulting dynamics. I illustrate with a variety of examples drawn from economics, sociology, demography, and political science. These include bargaining norms, norms governing the terms of contracts, norms of retirement, dueling, foot binding, medical treatment, and the use of contraceptives. These cases highlight the challenges of applying the theory to empirical cases. They also show that the modern theory of norm dynamics yields insights and predictions that go beyond conventional equilibrium analysis.