The Evolution of Social Norms

Social norms are patterns of behavior that are self-enforcing at the group level: everyone wants to conform when they expect everyone else to conform. There are multiple mechanisms that sustain social norms, including a desire to coordinate, fear of being sanctioned, signaling membership in the group, or simply following the lead of others. This article shows how stochastic evolutionary game theory can be used to study the dynamics of norms. We 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, duelling, footbinding, 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.