It is well known that patent citations occur disproportionately between patents issued to inventors living in the same location, which has been taken as evidence of geographically localized knowledge spillovers. In this study, we find that patent citations also occur disproportionately often in...

We examine the role of social relationships in facilitating knowledge flows by estimating the flow premium captured by a mobile inventor's previous location. Once an inventor has moved, they are gone - but are they forgotten? We find that knowledge flows to an inventor's prior location are...

Innovation is often predicated on discovering useful new combinations of existing knowledge in highly complex knowledge spaces. These needle-in-a-haystack type problems are pervasive in fields like genomics, drug discovery, materials science, and particle physics. We develop a...

The recruitment of foreign scientists enhances US science through an expanded workforce but could also cause harm by displacing better connected domestic scientists, thereby reducing localized knowledge spillovers. We develop a model in which a sufficient condition for the absence of overall...

The growing peer effects literature pays particular attention to the role of stars. We decompose the causal effect of hiring a star in terms of the productivity impact on: 1) co-located incumbents and 2) new recruits. Using longitudinal university department-level data we report that hiring a...

We report a puzzling pair of facts concerning the organization of science. The concentration of research output is declining at the department level but increasing at the individual level. For example, in evolutionary biology, over the period 1980 to 2000, the fraction of citation-weighted...