Patent citations reexamined
Corresponding Author
Jeffrey Kuhn
University of North Carolina at Chapel Hill
Corresponding author. Jeffrey Kuhn jeffrey_kuhn@kenan-flagler.unc.edu.Search for more papers by this authorCorresponding Author
Jeffrey Kuhn
University of North Carolina at Chapel Hill
Corresponding author. Jeffrey Kuhn jeffrey_kuhn@kenan-flagler.unc.edu.Search for more papers by this authorWe thank Ian Cockburn, Rui de Figueiredo, Jeff Furman, Michelle Gittelman, Dietmar Harhoff, Robert Merges, Michael Meurer, Atul Nerkar, Gaetan de Rassenfosse, Katja Seim, Tim Simcoe, Neil Thompson, Tony Tong, Andrew Toole, Brian Wright, Noam Yuchtman, and anonymous reviewers for helpful comments. We also thank seminar participants at the 2016 Searle Center Conference on Innovation Economics, the 2017 Boston University Law Schools Technology Policy and Research Initiative Conference, the 2016 Munich Summer Institute, the United States Patent and Trademark Office (2015), Skema Business School (2015), the 2016 DRUID Conference, and the 2016 Academy of Management Annual Meeting. The authors thank the United States Patent and Trademark Office for providing access to data. The authors also thank Google for a generous research grant of computing time on the Google Cloud.
Abstract
Many studies rely on patent citations to measure intellectual heritage and impact. In this article, we show that the nature of patent citations has changed dramatically in recent years. Today, a small minority of patent applications are generating a large majority of patent citations, and the mean technological similarity between citing and cited patents has fallen considerably. We replicate several well-known studies in industrial organization and innovation economics and demonstrate how generalized assumptions about the nature of patent citations have misled the field.
Supporting Information
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Data S1: Online Appendix Table 1: OLS estimates of backward citation counts. Table 2: OLS estimates of citation similarity over time. Figure 1. Mean citation similarity over time for citations from applications, examiners, both. Figure 2. Percentage of examiner citations by patent-level backward citation count. Figure 3. Citation-level plot of the mean number of times the cited patent appears as a citation across a patent family, by the family size of the citing patent. Figure 4. Patent-level plot of maintenance fee payments as a function of backward citation count. Figure 5. Total citations made by year, divided by number of backward citations made by citing family. Figure 6. Mean and interquartile range of citation Similarity by citing year, collapsed to family. Dot-dash is OLS estimate controlling for count of backward citations. Figure 7. Area plot of citations by backward citation count of citing patent family over time. Figure 8. Lorenz curves of cumulative proportion of families by backward citation count, by year. Figure 9. Mean and interquartile range of Similarity for citations by count of backward citations by citing family. Figure 10. Results from collapsing patent citation data to the family level. |
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