Arguably the most persistent questions in the literature on policy adoption and diffusion focus on the ways in which jurisdictions learn from one another in that process. Decades of research have offered many nuanced conclusions regarding the learning process, but many existing studies share a common trait that could limit the accuracy of those insights. The vast majority of studies infer learning indirectly by observing similarities between adopting states and the degree to which the effectiveness of a policy in one state predicts subsequent adoptions. Missing from these studies is direct evidence from policy makers regarding the places from which they gather information and the types of knowledge they seek when considering a policy innovation. 

This study compares direct versus indirect approaches to the measurement of learning. It draws on an extensive survey fielded by the authors of state legislators and agency officials responsible for crafting or implementing energy policy, which asked: how these actors gather policy information, which peers they turn to for information regarding energy policy innovation, and the degree to which this information influences policy choices in their states. We analyze these data using both social network analysis and traditional regression analysis in order to test whether the conclusions from the general literature on learning are compatible with those generated by our more direct measurement approach. We also compare the results from the survey with a traditional event history analysis of the diffusion of three recent sustainable energy policies about which respondents provided information on learning.