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 whether the distance between successive innovators has changed over time. We find the distance to be increasing slightly over time, both when considering all citations and only inter-city transfers.
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Title
Ain't No Sunshine When You're Gone: Analysis of the Knowledge Flows Between Successive Generations of Solar Innovations