Geographic Localization of Knowledge Spillovers as Evidenced by Patent Citations

Explores the geographic localization of knowledge spillover by comparing the location of inventors of citing patents to the location of the inventors of the patents they cite. The originating patents considered were from 1975 and 1980 and included all patents granted to U.S. universities and two samples from U.S. corporations. The citing patents were identified as of the end of 1989. Self-citations, that is when the owner of a cited patent is the same as the owner of the citing patent, are distinguished in this analysis. Results for the 1980 patents indicate that there is a definite and statistically significant pattern of localization at the country, state, and metropolitan statistical areas. The same pattern occurs for the 1975 patents, but it is at a weaker level. Further, the results show that localization fades over time though slowly. Technological area of the patent appears to have little impact on localization, nor is there a large difference in knowledge flows between patents held by universities and those held by corporations. Further investigation into the mechanisms of knowledge transfer is necessary, as this analysis was limited by the patent and citation data. (SRD)