Judging Equivalents

82 Pages Posted: 20 Aug 2019 Last revised: 16 Sep 2019

See all articles by Daryl Lim

Daryl Lim

University of Illinois at Chicago John Marshall Law School; Fordham University - Fordham Intellectual Property Institute

Date Written: August 16, 2019


Courts, patent attorneys, and legal scholars have wrestled with operationalizing the doctrine of equivalents for nearly 150 years. A venerable exception to normal patent infringement rules, the doctrine is deceptively simple to state – it enables patentees to reach beyond the literal wording of their claims, but it remains extremely controversial in its application. This Article provides an empirical basis for judges, scholars, policymakers, and patent attorneys to better understand the doctrine’s nature in order to contextualize its evolution and chart its future. It surveys the law and literature on the doctrine from its inception over 150 years ago to the present day, and reports on contemporary results that will interest these stakeholders. It tests conventional wisdom against 10,373 observable datapoints gleaned from 316 Federal Circuit and district court cases between 2009 and 2018, including Rule 36 summary affirmances with no opinion.

By coding the reasoning in each case, this Article reveals how district courts and the Federal Circuit employed the doctrine. Patent litigators would be interested practical questions such as what arguments are most likely to win? What role do factors like litigation venue, industry, and posture have on outcomes? The descriptive statistics in this Article provide useful insights into these questions and more. The results and conclusions of this study have immediate application to patent law and beyond. In doing so, this study contributes to evidence-based decision in patent law and policy by filling a significant gap in the literature.

The issues discussed in the article have been important and will remain so over time.

Keywords: Patent, doctrine of equivalents, empirical

Suggested Citation

Lim, Daryl, Judging Equivalents (August 16, 2019). Available at SSRN: https://ssrn.com/abstract=3438432 or http://dx.doi.org/10.2139/ssrn.3438432

Daryl Lim (Contact Author)

University of Illinois at Chicago John Marshall Law School ( email )

1200 W Harrison St
Chicago, IL 60607
United States

Fordham University - Fordham Intellectual Property Institute ( email )

150 West 62nd Street, Rm 7-145
New York, NY 10023
United States

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