Citation Overlap Proximity within the Triad : Evidence from Us and European Patent Citations

The aim of this paper is to investigate the correlation between the technological proximity measure based on patent citations in three economic areas: USA, Japan and the Europe. In each economic area, we use information from two international patent systems to construct the technological proximity for 240 international firms. In particular, we derive firms’ patent citations from United States Patent and Trademarks Office data and European Patent Office data. In order to compute the technological proximity, we follow the methodology developed by Mowery, Oxley, Silverman (1996, “Strategic alliances and inter-firm knowledge transfer,” Strategic Management Journal 17 (Winter special issue): 77-91) and Stuart, Podolny (1996, “Local search and the evolution of technological capabilities,” Strategic Management Journal 17 (Summer special issue): 21-38) which have introduced the citation overlap measure, an alternative way of evaluating proximity between firms. This index asks how many of the patents that one firm cites are also cited by another firm. It is worth noticing the asymmetric nature of this index, which makes it a convincing instrument to consider the knowledge flows between firms. The contribution to the existing literature is to analyse the robustness of the citation overlap proximity measure and the extent to which it can be influenced by patent systems