Knowledge is recognized as an important ingredient for economic growth in addition to physical capital and labor. While transforming knowledge into products and processes it is exploited commercially. Nevertheless, the existing knowledge stock and the absorptive capacity of actors like employees at firms and researchers at universities and research institutions are conditional for the ability to produce, identify, and exploit knowledge. Since incumbent firms do not exploit new knowledge to the full extent, realized entrepreneurial opportunities may arise. This paper tests the hypothesis whether or not entrepreneurship is an important vehicle for knowledge flows and economic growth. The empirical results indicate that an increase in innovative start-up activity is more effective than an increase in general entrepreneurship for economic growth.