Knowledge Spillovers Through a Patent Citation Analysis

The aim of this paper is to analyse the pattern of knowledge flows as evidenced by the patent citations in three economic areas: USA, Japan and Europe. In each economic area, we exploit information from two international patent offices data, the United States Patent and Trademarks Office data and the European Patent Office data. In this way, we can investigate the effect of technological proximity on knowledge spillovers for 240 international firms. In particular, the contribution to the existing literature is twofold: first, we use an international sample so that we can compare the empirical results among different economic markets; second, we explore the robustness the technological proximity effects and the extent to which it may be affected by patent system features. In order to compute the technological proximity, we consider both the symmetrical measure and asymmetrical one. The empirical results indicate that there is a statistically positive impact of technological proximity on knowledge spillovers measured by patent citations and that these results are robust with respect to patent office data used in the analysis