Where are the Eco-Innovators? Analysis of the Knowledge Flows between Successive Generations of Green Technology Innovations

This paper examines the location of innovations within green technology, using U.S. patent citation data to trace their inter-generational knowledge flows over time. Clustering is clearly evident, and we use multivariate left-censored Tobit regression analysis to control for identifiable factors, to show that the distance between successive innovators has not been rising over time. The interesting exception is nuclear energy in which distance appears to be decreasing over time. If we consider only inter-city transfers, the waste management also becomes more concentrated over time, while transportation declusters.