Geographic Localization of Knowledge Spillovers as Evidenced by Patent Citations
通过比较专利引用与被引专利的地理位置，发现国内专利引用更可能来自同一州或同一都市区，且这种本地化效应随时间缓慢减弱。
We compare the geographic location of patent citations with that of the cited patents, as evidence of the extent to which knowledge spillovers are geographically localized. We find that citations to domestic patents 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 frequency" reflecting the pre-existing concentration of related research 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 than others.