Exploring Changes in State Interest Group Systems: Replications and Extensions of the ESA Model

How have interest group populations in the fifty states changed in the 21st Century so far, and have factors like population growth, changing state ideology, economic performance, legislative professionalism, personal wealth, and shocks like the Great Recession shaped these changes? Using new data on state interest groups originally gathered by the National Institute for Money in State Politics, which I cleaned and introduced at last year, combined with several other measures of state politics, economic performance, and demographic change, I study these questions. With data covering the years 2006 to 2015 allowing for cross-state, as well as time-series, analysis, I explore the extent to which change in economic, political, and social variables lead to changes in state interest group systems, some of which replicates Gray and Lowery’s work. Their work holds-up well in the replications, but new extensions are also explored, including a new “capacity” term for the ESA model.