Interest group size dynamics and policymaking

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.     

A computational electoral competition model with social clustering and endogenous interest groups as information brokers

We extend the basic model of spatial competition in two directions. First, political parties and voters do not have complete information but behave adaptively. Political parties use polls to search for policy platforms that maximize the probability of winning an election and the voting decision of voters is influenced by social interaction. Second, we allow for the emergence of interest groups. These interest groups transmit information about voter preferences to the political parties, and they coordinate voting behavior. We use simulation methods to investigate the convergence properties of this model. We find that the introduction of social dynamics and interest groups increases the separation between parties platforms, prohibits convergence to the center of the distribution of voter preferences, and increases the size of the winning set.