The existing literature on the sources and nature of productivity growth during the early industrialization stages of U.S. has identified the combination of intellectual property rights (IPRs) with a large middle class and broad participation in markets as explanations for the extraordinary level and growth of patenting. The paper considers whether these factors could play a role in the contemporaneous evolution of innovation in a broad cross section of countries today.
Link
http://econwpa.wustl.edu:80/eps/dev/papers/0410/0410002.pdf