Out of Sight: Patents that Have Never Been Cited
27 Pages Posted: 16 Jul 2019
Date Written: July 15, 2019
Scientific understanding of innovation processes and of the patent system increasingly relies on big data analyses of patent citations. Much of that research focuses on highly cited patents. This study, conversely, offers the first systematic exploration of uncited patents — patents that receive no citations. Analyzing data on all US patents issued between 1976 and 2008, we focus on the ratio of uncited patents out of all patents granted each year. We track the changes in the percentage of uncited patents during that period, and across technological fields, controlling for patents’ age. We also investigate traits of uncited patents by examining the association between lack of citations and various factors including the number of inventors, number of technological subclasses, number of backward citations, and number of claims in the patent.
We find a robust pattern whereby the percentage of uncited patents declined between 1976 and the mid 1990s, but has been significantly increasing since then. These findings are consistent across technological fields and hold after controlling for patent characteristics. We discuss these and additional findings, and propose possible explanations. We suggest that the trend of increase in uncited patents raises, and reinforces, concerns regarding patent quality and “patent explosion”. More broadly, our focus on “negative information” embedded in patent data opens up a new avenue for further research that can deepen our understanding of the patent system.
Keywords: Uncited Patents, Patent Citations, Patent Quality, Negative Knowledge
JEL Classification: O3, O34
Suggested Citation: Suggested Citation