The evolution of social-movement organizations: Niche competition in social spate

Social-movement organizations compete with each other as do other organizations. Competition affects their success, and when facing competition, organizations must adjust. Thus, the evolution of social-movement organizations is influenced by other organizations in their environment. To study the dynamics of competition, this paper suggests that organizations compete for members. By using the analogy of the ecological niche, competition between social-movement organizations can be modelled with regard to the degree to which organizational niches overlap, with niche defined by characteristics of the organizations' members. Competition for members is studied in terms of growth and decline in membership. The niche dynamics of competition are investigated in terms of whether the size and location of organizational niches are interdependent over time. Some of the predictions are tested using data on the evolution of two Swedish social-movement organizations during the period 1915-34. The results are in line with the theoretical predictions of the paper: competition affects the ability of organizations to attract members, and competitive situations produce adjustments in the size and location of the niche.