Spatial convergence and spillovers in American invention

Endogenous growth theory places spatial knowledge spillovers at the center of national technological progress. Advances in spatial autocorrelation and regression analyses provide methods to assess the influence of these spillovers on the geographical distribution and growth of invention. This article investigates interstate inequality and convergence in per capita patenting in the United States in the period 1963-2003. We analyze both the complete forty years and trends in ten-year intervals. Moran's I reveals spatial dependence in patenting levels and growth, and LISA cluster maps identify regional groupings of leading and trailing states. Our regression results show that both regional effects and spatial spillovers influence convergence rates, which were low and steady in the thirty years before 1993. In the subsequent decade, patenting expansion concentrated in a few states, inequality increased, and divergence ensued. Western states, in general, and the Pacific Northwest, in particular, increasingly dominate patent growth. Rank order correlation analyses show that convergence before 1993 was driven by catch-up and not by leapfrogging. A final regression analysis shows that patent growth rates in the 1993-2003 interval were higher in more rural states and in those with high proportions of payrolls generated by high-technology manufacturing and producer services industries. States in the South significantly lagged. Our results support the hypothesis that creative skilled professionals seek to reside in states that offer both well-paying jobs in high-technology manufacturing and producer services sectors and easy access to rural outdoor recreation and leisure amenities.