Interest Group Influence in Policy Diffusion Networks

Abstract

Scholars have suggested that interest groups affect the diffusion of innovations across states by creating a network of information between the states that aids in the spread of policy ideas. Still, the unique role that interest groups play in policy diffusion networks is not fully understood, in large part because the current methodology for studying diffusion cannot parse out interest group influence. We address this problem by analyzing the actual text of legislation, moving away from binary adoption to a more nuanced measure of policy similarity. This allows us to distinguish whether states emulate other states or interest group model legislation. We use text similarity scores in a social network analysis to explore whether early-adopting states or interest groups are more central to the network. We apply this analytical framework to two policies—abortion insurance coverage restrictions and self-defense statutes. Based on this analysis, we find that a fundamentally different picture of policy diffusion networks begins to emerge—one where interest group model legislation plays a central role in the diffusion of innovations.