Testing a Dynamic Model of Social Composition: Diversity and Change in Voluntary Groups

We test a dynamic model of the social composition of voluntary groups. The model is based on the idea that sociodemographic variables define social niches in which voluntary groups grow and decline, share and compete, and change or remain static. The flow of individuals through such groups depends on the competition of other groups for their time and other resources. We build a dynamic model of this process and show how this model can account for changes in the social composition and the social heterogeneity of voluntary groups. We use life history data on the group affiliations of 1,050 individuals from 1974 to 1989 to test hypotheses about the diversity of education among group members and about the mean level of education of the members. Our data strongly support the hypotheses.