Patent Citations and the Size of the Inventive Step - Evidence from Hybrid Corn

Abstract

Patents are the main source of data on innovation, but there are persistent concerns that patents may be a noisy and biased measure. An important challenge arises from unobservable variation in the size of the inventive step that is covered by a patent. The count of later patents that cite a patent as relevant prior art-so called forward citations-have become the standard measure to control for such variation. Citations may, however, also be a noisy and biased measure for the size of the inventive step. To address this issue, this paper examines field trial data for patented improvements in hybrid corn. Field trials report objective measures for improvements in hybrid corn, which we use to quantify the size of the inventive step. These data show a robust correlation between citations and improvements in yields, as the bottom line measure for improvements in hybrid corn. This correlation is robust to alternative measures for improvements in hybrid corn, and a broad range of other tests.We also investigate the process, by which patents generate citations. This analysis reveals that hybrids that serve as an input for genetically-related follow-on inventions are more likely to receive self-citations (by the same firm), which suggests that self-citations are a good predictor for follow-on invention.

Patent Value and Citations: Creative Destruction or Strategic Disruption?

“…15 In additional regressions, not shown here, we find that the number of claims and dependent claims are statistically insignificant, which echoes recent findings by Moser, Ohmstedt, and Rhode (2012). Since there is a fixed cost to strategic patenting, those entities that hold more valuable patents should be more likely to engage in strategic patenting.…”

“…This approach is useful for understanding the distribution of patent value, but conveys little information for individual patents, in particular high-value patents, which is where we find the greatest deviation from the assumed monotonic citation-value relationship. In a more recent work, Moser, Ohmstedt, and Rhode (2012) link the forward citations of patents for hyrid corn with yields and find a positive correlation between the two. In a parallel study, Kogan, Papanikolaou, Seru, and Stoffman (2012) show that stock market response to news about patents is a good predictor of future forward cites.…”

Taxation and the International Mobility of Inventors

“…Constructing Quality Measures for Inventors.-Citations received have traditionally been used as measures of the economic and technological significance of a patent (see Pakes 1986;Schankerman and Pakes 1986;Trajtenberg 1990;Harhoff et al 1999;Hall, Jaffe, and Trajtenberg 2001;Bessen 2008;Kogan et al 2012;Moser, Ohmstedt, and Rhode 2015;Abrams, Akcigit, and Popadak 2013). We construct four different dynamic measures of the inventor's quality, which place different importance on the quantity versus value of an inventor's patents.…”

Patent citation data in social science research: Overview and best practices

“…Moser, Ohmstedt, and Rhode () identified specific improvements in hybrid corn and gathered data on the magnitude of the yield improvement they allowed. They interpret this as measuring the “inventive step” associated with the patent, but as the measurement is in the use domain rather than strictly in the technology domain it seems more closely related to social value than to inventive step, per se .…”