State Policy Innovation and Diffusion (SPID) Database v1.2

The SPID data include information on the year of adoption for over 700 policies in the American states. For each policy we document the year of first adoption for each state. Adoption dates range from 1691 to 2017 and includes all fifty states. Policies are adopted by anywhere from 1 to 50 states, with an average of 25 adoptions. The data were assembled from a variety of sources, including academic publications and policy advocacy/information groups. Policies were coded according to the Policy Agendas Project major topic code. Version 1.2 includes a small number of corrections to the previous version. These are summarized in the documentation and listed in the changes spreadsheet.