Membership in Citizen Groups

We address the coordination problem of individuals deciding to join an association that provides a public good and selective benefits to its members, when ability of the association to fulfill its purposes depends on membership size. In a global game formulation, we show that a unique equilibrium with non-trivial membership exists, and we perform meaningful comparative statics. A unique equilibrium also obtains when agents are heterogeneous, and we show that heterogeneity decreases membership size. In a two-period setting, where seniority of membership entails additional benefits, we provide conditions for uniqueness of equilibrium, and show that the presence of seniority benefits increases membership in both periods.