Policy Diffusion and the Pro-innovation Bias

Existing research on policy diffusion focuses almost exclusively on "successes" where many jurisdictions adopted the policy or policies under examination. Some have speculated that this "pro-innovation bias" compromises scholars' ability to draw valid inferences about the factors that influence the diffusion process. We argue that the study of interstate compacts in the United States provides an analytic opportunity to assess whether these concerns are warranted because it allows us to examine an entire universe of cases with unusually wide variability in their adoption patterns. Based on a pooled event history analysis of the interstate compacts that are open to all fifty states, we conclude that the tendency to limit diffusion research to widely adopted policies affects the results of previous studies. Specifically, it appears to lead scholars to systematically overestimate the impact of geographic diffusion pressures and policy attributes, and to underestimate the importance of professional associations and the opportunity to learn from previous adoptions. In sum, the longstanding concerns about a pro-innovation bias in diffusion research seem to be warranted.