Interest Group Survival: Shared Interests Versus Competition for Resources

Abstract

Population ecology theory on interest group populations is examined to determine the implications for group membership levels in the states. Using the assumptions of the competitive exclusion principle, it is hypothesized that relatively new interest groups should not directly compete for space, but should instead have a positive influence on each other's membership levels. A group's membership level should also be a function of space, energy, and political mobilization factors. Multiple regression analysis is applied to a fifty-state data set using the membership levels of five gay and lesbian interest groups as dependent variables. The hypotheses are confirmed—interest groups avoid direct competition for space by adapting into different issue niches. The results of these findings for a population ecology theory of interest groups are discussed along with directions for future research.