Epo vs. USPTO Citation Lags

This paper estimates the diffusion and obsolescence of technological knowledge by technological field, country and type of institutions that generates it. We use two comparable samples of patents and patent citations from the NBER U.S. Patent Citations Dataset (based on patents from the US Patent Office) and from the EP Cespri Dataset (based on patents from the European Patent Office). Using a quasi-structural model, as proposed by Caballero and Jaffe (1993) and discussed in Hall et al. (2001), we test whether the observed processes of knowledge diffusion and obsolescence reflect the specific institutional mechanism generating them. Results show that at the USPTO there are more citations per patent due to the different rules governing citation practices and that their median lag is twice as large relatively to the citations at the EPO. We also find that the relative properties of the citation frequencies in different technological fields change according to the patent office considered