Stars and comets: an exploration of the patent universe

The analysis of patent and citation data has become a popular source of evidence on localized knowledge spillovers and innovation. Nevertheless, an aspect has been overlooked: the patent distribution across inventors is extremely skewed, as many inventors register one or a few patents, while a small number of inventors register many patents. To our knowledge, the previous empirical literature has not discussed the different kinds of local innovation from which patents may originate. A first contribution of this paper is therefore to document the issue. A second contribution is to investigate whether patents originating from different scales of innovation are located in different cities. A third contribution - which constitutes the main scope of the paper - is to test whether the concentration of the activity of star inventors is beneficial to the local productivity of other kinds of innovation - namely the ones led by more occasional, and less prolific, inventors