Localized Knowledge Spillovers and Patent Citations: A Distance-Based Approach
开发了一种新的基于距离的本地化知识溢出检验方法，通过嵌入控制专利概念和使用微观地理数据，识别各技术类别的本地化距离，并发现即使采用精细控制，本地化现象依然显著存在。
We develop a new distance-based test of localized knowledge spillovers that embeds the concept of control patents. Using microgeographic data, we identify localization distance for each technology class while allowing for spillovers across geographic units. We revisit the debate between Thompson and Fox-Kean (2005a, 2005b) and Henderson, Jaffe, and Trajtenberg (2005) on the existence of localized knowledge spillovers and find solid evidence supporting localization even when using finely grained controls. Unless biases induced by imperfect matching between citing and control patents due to unobserved heterogeneity are extremely large, our distance-based test detects localization for the majority of technology classes.