Interest Group Size Dynamics and Policymaking (extensive revised version of WP 01-03)

Abstract

We present a dynamic model of endogenous interest group sizes and policymaking. The model integrates `top-down' (policy) and `bottom-up' (individual and social-structural) influences on the development of interest groups. Comparative statics results show that the standard assumption of fixed-sized interest groups can be misleading. Furthermore, dynamic analysis of the model demonstrates that reliance on equilibrium results can also be misleading since equilibria may be unstable. Complicated dynamics may then emerge naturally, leading to erratic time patterns for policy and interest group sizes. Our model can endogenously generate the types of spurts and declines in organizational density reported in empirical studies.