Dynamics of Religious Group Growth and Survival

Abstract

AbstractWe model and analyze the dynamics of religious group membership and size. A group is distinguished by its strictness, which determines how much time group members are expected to spend contributing to the group. Individuals differ in their rate of return for time spent outside of their religious group. We construct a utility function that individuals attempt to maximize, then find a Nash equilibrium for religious group participation with a heterogeneous population. We then model dynamics of group size by including birth, death, and switching of individuals between groups. Group switching depends on the strictness preferences of individuals and their probability of encountering members of other groups. We show that in the case of only two groups—one with finite strictness and the other with zero—there is a parameter combination that determines whether the nonzero strictness group can survive over time, which is more difficult at higher strictness levels. We also show that a high birth rate can allow even the strictest groups to survive. Finally, we consider cases of several groups, gaining insight into strategic choices of strictness values and displaying the rich behavior of the model.