The background to the authors’ question is the cottage industry that has grown up around research by economists that focuses on the analysis of patent citations. Generally speaking, researchers have used the number of citations that a patent receives in subsequent patents, which they call “forward citations” and which serve as a proxy measure for the “private” value of the patents for the owners. Elaborating on this notion of the private value of patents, researchers have taken patent citation counts as indicating the “quality”, “importance” and “impact” of these patents (though there does not appear to be any single agreed-upon understanding of what they these terms mean). Lurking behind this research is the assumption that there “ought to be a relationship between citations and value.” As stated by a leading figure in this field, Professor Manuel Trajtenberg, here, in a seminal 1990 paper on the topic, “[t]he presumption that citation counts are potentially informative of something like the technological importance of patents is thus well grounded.”
The authors question whether this presumption has in fact been shown by focusing on the assumption that patent examiners are in fact taking into account all (or at least a critical mass) of the submitted citations. Thus, as Campbell and Nieves concluded in a pioneering paper in 1979, patent citations are a better proxy for indicating patent quality that are citations in scientific publications because the examination citation is “evidence that the particular piece of prior art was examined as a possible reason for rejecting the patent applications in the first place and yet the patent application was accepted.” But how much of this assertion stands if there is reason to believe that applicant-submitted citations may not in fact to large extent by the examiner.
This is even more so given, as the authors note in a footnote,
“[a]s a practical matter, most validation studies find a positive association between forward citations and measures of value”. Although, in the battle of footnotes, the authors also observe that “[r]ecent work has also raised questions about the use of citations as indicator, because many of those patents turn out to be invalid and the process of adding those citations is quite complex” (citations omitted).All in all, given that size and momentum enjoyed by the patent citation cottage industry, it seems that it will take a lot to undermine its legitimacy.