Activist investors are shareholders that purchase large numbers of a public company's shares in an effort to effect a significant change within the company, often by trying to obtain seats on the company's board. A company can become a target of an activist if it is mismanaged, has excessive costs and could be run more profitably as a private company, or has another problem that the activist believes it can fix to make the company more valuable.

Here are the top activist investors in the U.S. based on assets under management (AUM) and the number of companies each activist has targeted between Jan. 1, 2017 and Oct. 13, 2020.

Data courtesy of Activist Insight. 

1. Elliott Management

  • Companies targeted since 2017: 64
  • AUM : $73.5 billion as of Dec. 31, 2019

Paul Singer founded Elliott Management in 1977 to focus on convertible arbitrage. Since then, the hedge fund diversified its strategies and became one of the most prolific activist investors in the world, targeting large global corporations like AT&T , Hyundai , and Softbank . Elliott also ventured into the world of private equity with its Evergreen Coast Capital arm, acquiring athenahealth , Barnes & Noble , and Travelport Worldwide .

In September, Elliott disclosed a 15% stake in Cubic, saying it partnered with a “leading private equity firm” – reportedly Veritas Capital – for a potential acquisition of the defense and transportation technology company.

2. Carl Icahn

  • Companies targeted since 2017: 18
  • AUM : $29.2 billion as of Dec. 31, 2018

Ever since his time as a “corporate raider” in the 1980s, Carl Icahn has been known as a pioneer of shareholder activism with the majority of his equity holdings still activist in nature. Icahn often focuses on targets with limited organic growth opportunities, excess cash on the balance sheet, and weak corporate governance.

In 2020, he launched a proxy contest at Occidental Petroleum, accusing the CEO of mismanagement over the company’s acquisition of Anadarko Petroleum. The activist also reportedly drove Xerox’s hostile takeover bid for HP and urged Volkswagen’s heavy-truck unit Traton to increase its takeover offer for Navistar International.

3. Third Point Partners

  • Companies targeted since 2017: 12
  • AUM : $21.1 billion as of June 18, 2020

Dan Loeb’s Third Point Partners “employs an event-driven, value-oriented investment style.” The firm, founded in 1995, seeks to identify situations where the activist can anticipate a catalyst that will unlock value. Third Point is a global investor, with campaigns at Campbell Soup, Sony, and Essilor Luxottica. Most recently, Third Point urged Walt Disney Co. to suspend its dividend and redirect those funds to its streaming service, saying the entertainment company must embrace the industry shift. Less than a week after Third Point’s position went public, Disney said it is reorganizing its media and entertainment division to give priority to its video streaming service.

4. Starboard Value

  • Companies targeted since 2017: 30
  • AUM : $5.9 billion as of Dec. 31, 2019

Since 2002, Jeffrey Smith’s Starboard Value has engaged with executives and directors to unlock shareholder value at undervalued companies. The activist broke barriers in 2014 when it successfully completed a full board sweep at Olive Garden parent company Darden Restaurants. Since then, Starboard has tried the same tactic at several other companies, including Newell Brands, Magellan Health, and GCP Applied Technologies, though it often settled ahead of the vote. 

Most recently, Starboard said it believed ON Semiconductor and agricultural science company Corteva have substantial opportunities to improve their performance, adding that the former might even become a potential takeover target. The activist also recently sponsored a $360 million special purpose acquisition company (SPAC) that seeks to target a company in the technology, healthcare, consumer, industrials, hospitality, or entertainment sectors.

5. ValueAct Capital

  • Companies targeted since 2017: 13
  • AUM : $12.3 billion as of Feb. 29, 2020

Since Jeff Ubben founded ValueAct Capital in 2000, the San Francisco-based activist fim has had representatives serve on the board of 41 companies, including Microsoft, Rolls-Royce, and Alliance Data Systems. The activist also committed to ESG investing with its Spring Fund, which held positions in Hawaiian Electric and AES Corp.

Earlier this year, Ubben stepped down as chief executive and handed the reins to Mason Morfit, who has served as chief investment officer since 2017. Ubben said he resigned as ValueAct’s leader to launch his ESG-focused fund, Inclusive Capital Partners, which is invested in Lindblad Expeditions, Enviva Partners, Nikola, and Unifi.

6. Trian Partners

  • Companies targeted since 2017: 9
  • AUM : $11 billion as of Dec. 31, 2019

Nelson Peltz founded Trian Partners in 2005 as a vessel to invest in “high quality but undervalued and underperforming public companies.” The activist seeks to work collaboratively with management teams and boards, but is not afraid to launch a proxy battle if needed. Most notably, Trian fought a proxy contest against Procter & Gamble in 2017 that cost the company a reported $100 million . Peltz won a seat on the board at a narrow margin of 0.0016%.

Most recently, Trian built 9.9% positions in asset managers Invesco and Janus Henderson and pushed the firms to consider a merger. Trian also began conversations with Comcast’s management after building a 0.4% stake in the entertainment giant worth $900 million.

7. Sachem Head Capital Management

  • Companies targeted since 2017: 11
  • AUM : $2.9 billion as of Dec. 31, 2019

Sachem Head was founded in 2012 by Scott Ferguson, a protégé of famed activist investor Bill Ackman. Over the last few years, Sachem Head has urged educational software company Instructure to explore strategic alternatives, pushed for the sale of education company 2U, and nominated four directors to the board of chemicals maker Olin Corp. Most recently, the activist built a $1.2 billion stake in Elanco Animal Health, saying the veterinary pharmaceutical company has opportunities to accelerate sales and improve its margins and R&D pipeline. The Edge Consulting Group dubbed Sachem Head “King of the Activists” in April. 

8. Pershing Square Capital Management

  • Companies targeted since 2017: 3
  • AUM : $9.2 billion as of March 1, 2020

After forming Pershing Square in 2003, Bill Ackman spent the last 17 years celebrating several highs as well as bouncing back from some deep lows. The activist first secured his reputation after successfully pressuring Wendy’s to spin off its Tim Hortons brand in 2004. Since then, Ackman launched a victorious proxy campaign against Canadian Pacific Railway, invested wisely in Starbucks, and saw a $27 million hedge turn into $2.6 billion following the stock market’s crash due to COVID-19.

Most recently, Ackman sponsored the largest-ever SPAC, raising $4 billion for the blank-check vehicle. Pershing Square Tontine is looking for “mature” unicorns that are private equity-sponsored, employee-owned, or family-controlled as potential targets for a merger, the activist said. 

9. Jana Partners

  • Companies targeted since 2017: 11
  • AUM : $2.2 billion as of Dec. 31, 2019

Barry Rosenstein’s JANA Partners is a value-oriented investor focused on shareholder engagement. Since 2001, the company has targeted several companies including Tiffany & Co., Whole Foods, and Conagra Brands. In 2018, JANA committed to focusing some investments on ESG issues and teamed up with the California State Teachers’ Retirement System (CalSTRS) to push tech giant Apple to do more about the iPhone’s effects on children. 

Earlier this year, JANA settled with restaurant group Bloomin’ Brands for two board seats. It also said it might discuss industry consolidation and board composition with the leadership team at government services company Perspecta.

10. Corvex Management

  • Companies targeted since 2017: 7
  • AUM : $2.5 billion as of Dec. 31, 2019

Launched by Keith Meister in 2011, Corvex Management uses an opportunistic methodology to make its stock picks: special situations, event-driven strategies, and value investing. Formerly Carl Icahn’s right-hand man, Meister has a controversial investing style that is outspoken and ornery, much like his former boss.

One of Corvex’s most successful activist endeavors was at Yum! Brands in 2015, where Meister gained a board seat and convinced the company to spin off its Chinese division. Corvex also successfully pushed Energen to sell itself to Diamondback Energy in 2018.

Most recently, Meister said the utilities sector is a sensible place to invest, pitching Exelon Corp as a favorite defensive play because it is cheap, well-positioned, and likely to see internal changes in the nearterm.