GEOGRAPHIC LOCALIZATION OF KNOWLEDGE SPILLOVERS AS EVIDENCED BY PATENT CITATIONS

We compare the geographic location of patent citations with that of th e cited patents, as evidence of the extent to which knowledge spillove rs are geographically localized. We find that citations to domestic pa tents are more likely to be domestic, and more likely to come from the same state and SMSA as the cited patents, compared with a ''control f requency'' reflecting the pre-existing concentration of related resear ch activity. These effects are particularly significant at the local ( SMSA) level. Localization fades over time, but only very slowly. There is no evidence that more ''basic'' inventions diffuse more rapidly th an others.