The Rise of Anti-Activist Poison Pills

49 Pages Posted: 24 Aug 2022

See all articles by Ofer Eldar

Ofer Eldar

Duke University School of Law; Duke University - Fuqua School of Business; Duke Innovation & Entrepreneurship Initiative

Tanja Kirmse

Drexel University

Michael D. Wittry

Ohio State University (OSU) - Department of Finance

Date Written: August 22, 2022


We create a novel dataset of the terms of poison pill plans to examine their prevalence over time. Consistent with the hypothesis that poison pills have responded to the increase in hedge fund activism, recent adoptions have characteristics and provisions that appear to target hedge funds, such as low trigger thresholds. Moreover, using unique data on activist hedge fund views of SEC filings as a proxy for the mere threat of an activist intervention, we show that hedge fund interest strongly predicts pill adoption. Finally, the likelihood of a 13D filing declines after firms adopt “antiactivist” pills. Our analysis has implications for understanding the modern dynamics of market discipline of managers in public corporations, and evaluating policies that regulate defensive tactics.

Keywords: Poison pills, activism, hedge funds, market for corporate control, takeovers

JEL Classification: G30, G34, K22

Suggested Citation

Eldar, Ofer and Kirmse, Tanja and Wittry, Michael D., The Rise of Anti-Activist Poison Pills (August 22, 2022). Fisher College of Business Working Paper No. 2022-03-007, Charles A. Dice Center Working Paper No. 2022-07, Duke Law School Public Law & Legal Theory Series No. 2022-48, Available at SSRN: or

Ofer Eldar

Duke University School of Law ( email )

210 Science Drive
Box 90362
Durham, NC 27708
United States

Duke University - Fuqua School of Business ( email )

Box 90120
Durham, NC 27708-0120
United States

Duke Innovation & Entrepreneurship Initiative ( email )

215 Morris St., Suite 300
Durham, NC 27701
United States

Tanja Kirmse

Drexel University ( email )

3141 Chestnut St
Philadelphia, PA 19104
United States

Michael D. Wittry (Contact Author)

Ohio State University (OSU) - Department of Finance ( email )

854 Fisher Hall
2100 Neil Avenue
Columbus, OH 43210-1144
United States
614-292-3217 (Phone)


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