The economics literature clearly shows that the transmission of knowledge diminishes with physical distance, a factor contributing to industrial clustering. This paper investigates how those distances have stretched over time. We measure the physical distance between collaborating inventors, as...

Using patent citation data for the U.S., we test whether knowledge spillovers in biotechnology are sensitive to distance. Controlling for self-citation by inventor, assignee and examiner, cohort-based regression analysis shows that spillovers are local but that distance is becoming less...

We model the diffusion of economic knowledge using an epidemiological model of susceptible, exposed, infected, and recovered populations (SEIR). Treating bibliographic citations as evidence of contagion, we estimate the coefficients of a four-equation system simultaneously for each of 759...

This paper examines the location of innovations within solar technology, using U.S. patent citation data to trace their diffusion over time. Knowledge clustering is clearly present. We employ multivariate left-censored Tobit regression analysis to control for identifiable factors, to examine...

Using over 200,000 U.S. patent citations, we test whether knowledge transfers in the transportation sector are sensitive to distance, and whether that sensitivity has changed over time. Controlling for self-citation by inventor, assignee and examiner, multivariate regression analysis shows that...

The economics literature clearly shows that the transmission of knowledge diminishes with physical distance, a factor contributing to industrial clustering. This paper investigates how those distances have stretched over time. We measure the physical distance between collaborating inventors, as...

This paper examines the evidence on the clustering of innovators within the telecommunications sector, using U.S. patent citation data to trace their locations over time. While clustering is clearly evident, we use multivariate left-censored Tobit regression analysis to control for identifiable...