FLOWS OF KNOWLEDGE FROM UNIVERSITIES AND FEDERAL LABORATORIES - MODELING THE FLOW OF PATENT CITATIONS OVER TIME AND ACROSS INSTITUTIONAL AND GEOGRAPHIC BOUNDARIES

The extent to which new technological knowledge flows across instituti onal and national boundaries is a question of great importance for pub lic policy and the modeling of economic growth. In this paper we devel op a model of the process generating subsequent citations to patents a s a lens for viewing knowledge diffusion. We find that the probability of patent citation over time after a patent is granted fits well to a double-exponential function that can be interpreted as the mixture of diffusion and obsolescense functions. The results indicate that diffu sion is geographically localized. Controlling for other factors, withi n-country citations are more numerous and come more quickly than those that cross country boundaries.