Benefiting Colleagues but not the City: Localized Spillovers from the Relocation of Superstar Inventors

In this paper I analyze spillover effects on the production of patents following episodes in which superstar inventors relocate to a new city. In particular, in order to distinguish whether local externalities have a restricted network dimension or a wider spatial breadth, I estimate changes in patterns of patenting activity for two different groups of inventors: the restricted group of coauthors of the superstar, and all other inventors in one urban area. The analysis is performed for both the locality where the superstar moves and the one that is left. I restrict the attention to patent outputs that exclude any joint work with the superstar, so to isolate spillovers from complementarity effects. The results from the event study evidence a large and persistent positive effect on the coauthors of the superstar who reside in the city of destination (averaging about 0.1 more patents per inventor each year), and a negative trend affecting those who live in the locality of departure. These effects increase with the relative ranking of the superstar in the patent distribution. Conversely, no city-wide spillover effect can be attested, offering little support to place-based policies aimed at generating a positive local agglomeration of human capital.