Stars and Comets : An Exploration of the Patents Universe

The analysis of patent and citation data has become a popular source of evidence on localized knowledge spillovers and innovation. Nevertheless, one aspect has been overlooked: the patent distribution across inventors is extremely skewed, as many inventors - the comets - register one or few patents, while a small number of inventors - the stars - register many patents. This raises a number of questions relating to the geography of innovation: do different categories of inventors interact with the local economic environment in the same way? Are they equally distributed over space or do they tend to concentrate? Is spatial proximity bene cial for their activity? Using a rich database on US inventors, we provide evidence suggesting that the two categories of patents are associated with different kinds of cities. We then test whether the activity of stars is bene cial for local comets, finding that a 10% increase in the number of patents authored by star inventors leads approximately to a 1% increase in the number of patents developed by comet inventors