ON THE EDGE OR IN BETWEEN - NICHE POSITION, NICHE OVERLAP, AND THE DURATION OF VOLUNTARY ASSOCIATION MEMBERSHIPS

This paper aims to explain a major barrier to societal integration: th e remarkable homogeneity of voluntary associations. The explanation de rives from an ecological theory of voluntary affiliation that asserts that organizations compete for members in a property space defined by the sociodemographic characteristics of members. Voluntary organizatio ns lose fastest those members who are either atypical of the group (th e niche edge hypothesis) or subject to competition from other groups ( the niche overlap hypothesis). The authors analyze an event-history da ta set, generated by the life-history calendar approach, of 2,813 volu ntary association membership spells. The results, which strongly suppo rt both the niche edge and niche overlap hypotheses, substantiate the competitive ecological model of group structure.