Most Talked-About Controversies Linked to Bill Ackman

By Popular Timelines Editorial Team · Updated: July 19, 2026

Controversies are a part of history. Explore the biggest scandals linked to Bill Ackman.

Bill Ackman is a prominent American billionaire investor and the founder and CEO of Pershing Square Capital Management. He is widely recognized for his activist investing style, where he takes significant stakes in companies to advocate for operational or management changes to unlock shareholder value. Throughout his career, Ackman has been involved in several high-profile financial campaigns, including his notable short position against Herbalife and his successful long-term investment in Canadian Pacific Railway. Beyond his investment firm, Ackman is known for his public commentary on economic policy, corporate governance, and various social issues, frequently utilizing social media to influence discourse. His investment strategy often involves concentrated portfolios and deep research, making him one of the most influential figures on Wall Street. Despite periods of volatility in his fund's performance, he remains a key figure in modern finance and a vocal advocate for his investment theses.

Sections (5)

Full Timeline Early Life & Education Career & Achievements Challenges & Struggles Controversies & Scandals

2002: Gotham Partners Litigation

By 2002, the investment firm Gotham Partners became heavily involved in legal conflicts and litigation with other shareholders who shared interests in the firm's portfolio companies.

2002: Challenge to MBIA Credit Rating

In 2002, Bill Ackman conducted extensive research into MBIA to contest the AAA bond rating provided by Standard & Poor's. During this process, his legal team incurred over $100,000 in costs to process 725,000 pages of financial documents under subpoena, and Ackman publicly advocated for the structural separation of MBIA's municipal bond and structured finance divisions.

2011: Initiation of Canadian Pacific Railway Proxy Contest

In 2011, Bill Ackman's firm, Pershing Square, started accumulating shares in the Canadian Pacific Railway. By November 2011, citing lackluster financial performance, Ackman launched a proxy contest to overhaul the company's leadership team, specifically targeting the CEO and board members.

December 2012: Short Bet Against Herbalife

In December 2012, Bill Ackman announced that his firm, Pershing Square, had executed a $1 billion short position against Herbalife, publicly characterizing the supplement company as a pyramid scheme.

2012: Initiation of Herbalife Short Position

In 2012, Bill Ackman began a high-profile one billion dollar short position against Herbalife, publicly denouncing the organization as a pyramid scheme.

January 2013: Carl Icahn Announces Herbalife Stake

Following a heated public confrontation on CNBC, investor Carl Icahn announced in January 2013 that he had purchased a stake in Herbalife, effectively opposing Ackman's short position.

August 2013: Ackman Resigns from J. C. Penney Board

In August 2013, Bill Ackman ended his two-year campaign to restructure J. C. Penney by resigning from the company's board of directors following internal conflicts with other board members.

April 2014: FBI Investigation into Herbalife

In April 2014, it was reported by Reuters that the FBI had initiated an investigation into Herbalife, which involved the review of documents gathered from the company's former distributors.

March 12, 2015: Probe into Pershing Square Tactics

On March 12, 2015, reports surfaced that federal authorities and the FBI were investigating whether individuals hired by Bill Ackman provided false information to regulators in an attempt to manipulate Herbalife's stock price.

April 27, 2016: Testimony before the U.S. Senate Special Committee on Aging

On April 27, 2016, Bill Ackman appeared before the United States Senate Special Committee on Aging alongside J. Michael Pearson and Howard Schiller to address concerns regarding the business practices and drug pricing strategies of Valeant Pharmaceuticals.

2018: Conclusion of Herbalife Short Position

By 2018, Bill Ackman concluded his significant multi-year short position against the nutrition firm Herbalife, a battle which was later documented in the film Betting on Zero.

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March 18, 2020: Call for Economic Shutdown during COVID-19

On March 18, 2020, Bill Ackman gave an emotional interview on CNBC urging President Donald Trump to initiate a 30-day shutdown of the U.S. economy to mitigate the impacts of the coronavirus pandemic, warning of severe economic consequences including failing hotel stocks and urging companies to halt stock buybacks.

2024: Bill Ackman Endorses Donald Trump and Addresses Geopolitical and Campus Issues

In 2024, Bill Ackman, historically a donor to Democratic causes, shifted his political stance by endorsing Donald Trump for the United States presidency. Additionally, in 2024, Ackman maintained a strong public stance in support of Israel following the October 7 attacks and vocalized criticism regarding pro-Palestinian protest movements occurring on various university campuses.