The evolution of legislative jurisdictions

We consider the clarity of the jurisdictions of the committees of the U.S. Congress over the entire post-war period. We offer a theory to explain changes in clarity over time, emphasizing how the rise of new issues and the redefinition of existing ones undermine the clarity and stability of committee jurisdictions. We present results from a new dataset on all congressional hearings between 1947 and 1994-67,291 cases in all. Using new summary indices of jurisdictional clarity, we trace the evolution of the jurisdictional system for both the House and Senate. We demonstrate low levels of clarity for most issues and a decline in clarity for the system as a whole over time. Further, we show that these developments are the result of changes in issue-density (the rise of new issues and the redefinition of old ones) and increases in institutional resources, in particular professional committee staff, We note the implications of these findings for models of legislative behavior and government decision-making more generally.