Patenting Fast and Slow: Examiner and Applicant Use of Prior Art

44 Pages Posted: 2 Mar 2020 Last revised: 15 Oct 2020

See all articles by S. Sean Tu

S. Sean Tu

West Virginia University College of Law

Date Written: February 14, 2020


Previous studies have shown that an applicant’s ability to obtain a patent is inexorably linked to the random assignment of a patent examiner. However, not all patent examiners are created equal. Some patent examiners allow patent applications quickly within just one or two Office Actions resulting in only a few months of substantive patent prosecution. In contrast, other patent examiners constantly reject patents applications, which can result in unnecessarily delaying prosecution and years of substantive patent prosecution. This study focuses on how different examiners use prior art rejections to prolong or compact prosecution.

Prior art rejections are one of the most important hurdles to obtaining a patent. Specifically, the use of prior art rejections directly impacts the time and effort it takes to obtain a patent. Overcoming anticipation and obviousness rejections are usually the most important and difficult obstacles to overcome before obtaining a patent. This empirical study focuses on how different types of examiners (i.e., fast/high volume versus slow/low volume) use prior art rejections to either compact or delay prosecution. Since patent examination is dependent on both examiner and applicant behavior, this study also evaluates how applicants respond to these prior art rejections to also prolong or compress prosecution. Unlike many studies, this is the first paper that evaluates patent quality based on both individual examiner characteristics as well as applicant behavior at the patent prosecution level.

In sum, high volume, average volume and low volume examiners issued a patent in approximately 1.64 years, 3.07 years, and 5.85 years respectively. Thus, high volume examiners issue patents almost twice as quickly as average volume examiners and more than three times as fast as low volume examiners. This large difference in time can represent a huge investment in both capital and time for the applicant as well as the PTO.

Additionally, this study finds that low volume examiners reject applications based mainly on obviousness, issuing over four times as many obviousness rejections per office action compared to high volume examiners. Furthermore, low volume examiners issue five times as many 102(a)/(g)/(e) rejections and two times as many 102(b) rejections. And applicants most commonly make a “missing element” argument to traverse a slow examiner’s 102(a)/(g)/(e) rejection at three times the rate of a fast examiner. This type of traversal strategy relies on the examiner’s misunderstanding of either the art or the claimed invention. Similarly, applicants also use the “missing elements” argument to traverse a slow examiner’s 103 rejection at five times the rate of a fast examiner. Finally, applicants are also three times more likely to use a “teaching away” or “unexpected results” argument to traverse a slow examiner compared to a fast examiner. Both of these arguments can again rely on either the examiner’s misunderstanding of the prior art or a misunderstanding of the claimed invention.

This study demonstrates that different types of examiners use different strategies to maximize their “counts.” Specifically, low volume examiners will generally reject applications creating lengthy prosecution histories while forcing the applicant to narrow claims, while showing a misunderstanding of either the prior art and/or the claimed invention. In contrast, high volume examiners will usually only make one rejection then allow the case, thus creating a small prosecution history with only small amendments to the claims.

Keywords: patents, patent examiner, patent prosecution, prior art, prior art rejections, patent quality, applicant response, applicant behavior, PTO

JEL Classification: K10

Suggested Citation

Tu, Shine (Sean), Patenting Fast and Slow: Examiner and Applicant Use of Prior Art (February 14, 2020). Cardozo Arts & Entertainment Law Journal, Volume 38(2): 391-434 (2020), WVU College of Law Research Paper 2020-004, Available at SSRN: or

Shine (Sean) Tu (Contact Author)

West Virginia University College of Law ( email )

101 Law School Drive
Morgantown, WV West Virginia 26506
United States

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