The population ecology of interest groups and counter-mobilization: reproductive rights organizations in the United States, 1920–1985

This research note builds upon a number of important articles published in a variety of outlets concerning the population ecology of interest groups. Importantly, Lowery and Gray (1995), Nownes (2004), and Nownes and Lipinski (2005) empirically demonstrated the dependence on the density of pre-existing, similar groups when predicting new group formations. In this letter, I add to this research by modeling the density of ideologically divergent reproductive rights groups as well as offer supporting evidence for the popular Energy-Stability-Area model. The former is a novel consideration in the field of population ecology which primarily examines ideologically similar groups. I show that density dependence is at play among these polarized groups. I also provide insight into counter-mobilization movements of group formation by empirically demonstrating which groups are initial movers versus reactionary formers. In doing so, I raise important questions for researchers concerned with the emergence, longevity, and impact of interest groups over long periods of time. Finally, this research provides some insight into the expectations of group formation behavior in light of the landmark Dobbs decision.