Why amicus curiae cosigners come and go: A dynamic model of interest group networks

Abstract

Interest groups use coalition strategies to exert influence, yet, like other political actors, they also withdraw from partnerships in the pursuit of other policy goals. We explore how interest group coalition strategies have changed over time and which factors determine whether interest groups relationships form and dissolve. Utilizing dynamic networks of a panel of interest groups derived from cosigner status to United States Supreme Court amicus curiae briefs, we illuminate the evolution of the social networks of frequent signers from the 1970s to the present day. A separable temporal exponential random graph model (STERGM) shows that the number of partners is important for formation but not dissolution, while industrial homophily helps both to make and maintain connections. In addition, statistical trends suggest that while networks change, a few players have acted continuously as coordination hubs for the bulk of the decades. However, a number of other key players in particular decades would be missed without a dynamic perspective.