Abstract
The extent to which new technological knowledge flows across
institutional and national boundaries is a question of great importance
for public policy and the modeling of economic growth. In this paper we
develop a model of the process generating subsequent citations to
patents as 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 diffusion is geographically localized. Controlling for other
factors, within-country citations are more numerous and come more
quickly than those that cross country boundaries.