This paper presents results of simulation models of democratic government in voluntary organizations. The models explore the impact of changes in the institutions that control exit and entry into the organization as well as some basic parameters that determine the distribution of preferences. Results indicate the following. First, democratically governed groups evolve in ways that are not predictable from information about the nature of the preferences in the society from which they are drawn. Rather, the long-run membership and policy stances of a group depend on an intricate evolutionary process that links membership adjustments with democratically determined policy shifts. Second, the evolutionary process is significantly affected by the overall willingness of people to join groups as well as the way that people are selected to participate in the group's first meetings. The implications for the formation of new interest groups are discussed.
