Much extant research on the distribution of power in the American federal system is drawn from qualitative case studies of particular acts of government. This often limits the empirical testing of generalizable hypotheses. To address this shortcoming, we develop an aggregate time series measure of policy centralization by the U.S. federal government for the 1947-1998 annual period utilizing relevant public laws and executive orders. On a substantive level, the data provide quantitative information regarding the willingness of the national government to delegate policymaking responsibility to state governments. This, in turn, can be used to assess the distribution of powers between governmental levelsa subject that has received little systematic inquiry to date. These measures indicate that although U.S. national government policymaking authority has risen in an overall sense during the postwar period vis--vis subnational counterparts, it has not grown monotonically over time. Contrary to existing descriptive accounts, the data also show that neither Nixon nor Reagans New Federalism initiatives intended to delegate or decentralize policymaking authority to subnational governments have succeeded in igniting systemic, persistent devolution in American federalism.
