How Do I Know What You Know? Patent Examiners and the Generation of Patent Citations

Analysis of patent citations is a core methodology in the study of knowledge diffusion, and forward citations are used as a measure of impact of innovations. However, citations made by patent examiners have not been separately reported, adding unknown noise to the data. We leverage a recent change in the reporting of patent data showing citations added by examiners. The magnitude is high: examiners add 40 per cent of all citations and two-thirds of citations on the average patent are inserted by examiners. Furthermore, 40 per cent of all patents have all citations added by examiners. We analyse the distribution of examiner and inventor citations with respect to self-citation, distance, technology overlap, and vintage. Results indicate that inferences about inventor knowledge may suffer from bias or overinflated significance levels. For a cohort of very highly-cited patents, examiners and inventors select different patents for citation, with the majority of the cohort cited by inventors. Over time, inventor and examiner forward citation streams converge, suggestive of a learning process that has not been previously considered in the literature