The evolution of specialization in the EU15 knowledge space
利用专利分类数据构建知识空间，分析1981至2005年欧盟15国区域知识专业化的演变，分解技术进入、退出和选择过程对专业化的贡献。
Significant attention has been directed to processes of knowledge production, but little consideration has been given to the type of technological knowledge produced within specific places. Patent co-classification data are employed to measure the distance between all pairs of International Patent Classification categories in order to visualize and to trace the evolution of the EU15 knowledge space from 1981 to 2005. Technological relatedness measures specify the degree of specialization of knowledge produced within each NUTS2 region. Knowledge specialization has increased significantly across regions since 1981. Changes in the average relatedness of regional knowledge cores are decomposed to reveal the contributions of technological entry, exit and selection processes over space and time. In a final section of the paper, technological diversification and abandonment at the regional level are modeled as a function of proximity to the knowledge core of the region and to knowledge spillovers from neighboring regions.