Mobility of skilled workers and co-invention networks: an anatomy of localized knowledge flows
利用美国发明家在欧洲专利局的专利数据，结合专利引用和社会网络分析，发现控制发明人流动和共同发明网络后，地理邻近性对知识扩散的影响大幅减弱，说明地理限制知识扩散的根本原因是流动研究者不愿远距离迁移。
This article illustrates the contribution of mobile inventors and networks of inventors to \nthe diffusion of knowledge across firms and within cities or states. It is based upon an \noriginal data set on US inventors’ patent applications at the European Patent Office, \nin the fields of drugs, biotechnology and organic chemistry. The study combines the \nmethodology originally proposed by Jaffe et al. (1993, Quarterly Journal of Economics, \n108: 577–598) with tools from social network analysis, in order to evaluate extent of \nthe localization of knowledge flows, as measured by patent citations. After controlling \nfor inventors’ mobility and for the resulting co-invention network, the residual effect of \nspatial proximity on knowledge diffusion is found to be greatly reduced. We argue that \nthe most fundamental reason why geography matters in constraining the diffusion of \nknowledge is that mobile researchers are not likely to relocate in space, so that their \nco-invention network is also localized. In the light of these results, we revisit common \ninterpretations of localized knowledge flows as externalities.