Seminario Policymaking in the American States, 1787-2020

Abstract

The U.S. federal system is often described as a set of “laboratories of democracy,” yet the structure of policy diffusion across states and between states and the federal government is difficult to measure. We compile the universe of state statutes from 1787–2020 (2.5 million acts) together with all federal statutes, extract distinct policy adoptions (7.9 million) using large language models, and group policies into clusters based on their legal content. We estimate a discrete-choice model of state and federal policy cluster adoption in which each jurisdiction’s decision depends on local conditions as well as horizontal (interstate) and vertical (state-federal) diffusion dynamics. Horizontal diffusion is allowed to vary with geographic, economic, and political alignment between states. To address unobserved correlated shocks, we conduct a range of robustness analyses; in particular, our estimates remain stable under progressively stricter fixed effects, including state-pair × policy × year effects. We also exploit plausibly exogenous variation in peers’ adoption arising from cross-legislature differences in observable characteristics. Geography dominates horizontal diffusion through the mid-twentieth century, economic similarity has a positive and relatively stable effect throughout, and partisan alignment increases sharply after the 1990s but remains comparable to historical levels. Finally, federal legislative activity becomes increasingly predictive of subsequent state legislation after World War II and now exceeds that of any single state, while the predictive relationship from state legislative activity to federal legislation has declined over time.