The evolution of networks of innovators within and across borders: Evidence from patent data
利用1988-2009年OECD国家欧洲专利局数据，分析物理距离和国家边界对四种创新网络（合作发明、专利引用、发明人流动、研发实验室选址）的影响，发现距离和边界的约束在1990年代中期前减弱，之后增强。
Recent studies on the geography of knowledge networks have documented a negative impact of physical distance and institutional borders upon research and development (R&D) collaborations. Though it is widely recognized that geographic constraints and national borders impede the diffusion of knowledge, less attention has been devoted to the temporal evolution of these constraints. In this study we use data on patents filed with the European Patent Office (EPO) for OECD countries to analyze the impact of physical distance and country borders on inter-regional links in four different networks over the period 1988–2009: (1) co-inventorship, (2) patent citations, (3) inventor mobility and (4) the location of R&D laboratories. We find the constraint imposed by country borders and distance decreased until mid-1990s then started to grow, particularly for distance. The intensity of European cross-country inventor collaborations increased at a higher pace than their non-European counterparts until 2004, with no significant relative progress thereafter. For geographical networks of mobility, R&D activities and patent citations we cannot detect any substantial progress in European research integration above and beyond the common global trend.