The central problem in understanding economic development and growth is not, in fact, to understand the process by which an economy raises its savings rate and increases the rate of physical capital accumulation. Many development practitioners and researchers continue to target capital accumulation as the driving force in economic growth. This paper, however, presents evidence regarding the sources and patterns of economic growth, the patterns of factor flows, and the impact of national policies on economic growth that suggest that something other than capital accumulation is critical for understanding differences in economic growth and income across countries.