Measuring R & D spillovers : on the importance of geographic and technological proximity

Evidence is presented which suggest that an important measure of the apparent geographic localization of R&D spillovers may be an artifact of industrial agglomeration. A production function framework is used to examine the role of geographic and technological proximity for inter-firm spillovers from R&D. The largest spillovers are found to flow between firms in the same industry. However, spillovers within narrowly defined technological groups do not appear to be attenuated by distance. Geographic proximity does appear to attenuate spillovers that cross narrowly defined technological boundaries, suggesting these spillovers may play a role in the agglomeration of a diversity of industrial activity.