Our More-Than-Twenty-Year Patent Term

52 Pages Posted: 3 Aug 2023 Last revised: 14 Dec 2023

See all articles by Mark A. Lemley

Mark A. Lemley

Stanford Law School

Jason Reinecke

Marquette University - Law School

Date Written: July 31, 2023


Since 1995, patents in the United States expire twenty years from the day they were filed. Except when they don’t. Beginning in 2000, Congress provided certain “exceptions” to the twenty-year patent term, extending the life of patents to compensate for excessive delays in patent prosecution or for successful appeals or certain other proceedings. This is called “patent term adjustment” (PTA).

Those exceptions have swallowed the rule. In this Article, we study all of the nearly 4.5 million patents filed on or after May 29, 2000 that issued by the United States Patent and Trademark Office since 2005. We find that most patents (63.6%) get at least some PTA. The patents that do get PTA get more than a year on average (411 days, a median of 290 days), and more than 25% of all patents have more than a year of extra term. Some get as much as ten years of extra term.

PTA ensures that patentees don’t lose term because of delays in the patent office. But it isn’t full compensation; an extra year at the end of a patent’s life is not as good as an extra year at the beginning for most patent owners. There is some double-counting, resulting in some patent owners getting more patent term than they logically deserve. And the PTA system ends up disproportionately being used by patent trolls in litigation, a result that seems socially unproductive.

Despite its imperfections and some suggestions we have for reform, the PTA system works pretty well at achieving the goal of compensating patentees for patent prosecution delay. But we would be better off with a world in which delay wasn’t nearly as common as it is. We offer some suggestions for how to reduce delay and the PTA that results.

Keywords: intellectual property, patents, empirical legal studies

Suggested Citation

Lemley, Mark A. and Reinecke, Jason, Our More-Than-Twenty-Year Patent Term (July 31, 2023). Stanford Law and Economics Olin Working Paper No. 586, Available at SSRN: https://ssrn.com/abstract=4529670 or http://dx.doi.org/10.2139/ssrn.4529670

Mark A. Lemley (Contact Author)

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305-8610
United States

Jason Reinecke

Marquette University - Law School ( email )

Eckstein Hall
P.O. Box 1881
Milwaukee, WI 53201
United States

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