• Home
  • Latest
  • Fortune 500
  • Finance
  • Tech
  • Leadership
  • Lifestyle
  • Rankings
  • Multimedia

Trendingnow

1

Trump, who has repeatedly called climate change fake, is now threatening Brazil with tariffs over the deforestation of the Amazon

2

Current price of oil as of June 8, 2026

3

'We didn’t see this coming': Wall Street eats its forecasts as stocks sell off globally on fear of AI bubble ahead of SpaceX IPO

1

Trump, who has repeatedly called climate change fake, is now threatening Brazil with tariffs over the deforestation of the Amazon

2

Current price of oil as of June 8, 2026

3

'We didn’t see this coming': Wall Street eats its forecasts as stocks sell off globally on fear of AI bubble ahead of SpaceX IPO
FinanceInvestors Guide

What the drop in Valeant’s stock says about hedge funds’ herd mentality

By
Stephen Gandel
Stephen Gandel
Down Arrow Button Icon
By
Stephen Gandel
Stephen Gandel
Down Arrow Button Icon
October 25, 2015, 12:37 PM ET
Hedge fund manager Bill Ackman
Bill Ackman, CEO and founder of Pershing Square Capital Management, at the 2015 Delivering Alpha on July 15, 2015.Photograph by David A.Grogan—CNBC/NBCU/Photo Bank via Getty Images

Bill Ackman, the famously outspoken hedge fund manager, has lost roughly $2 billion, on paper, on his investment in Valeant, the controversial drug company that plunged this past week after a short seller compared it to Enron. It was Ackman’s fund’s largest holding.

But he is certainly not alone among the losers. A number of large hedge funds were also significant holders of Valeant as recently as the middle of the year. Among the others who could be out big bucks are the funds of John Paulson, who made billions betting against the housing market, and activist investor Jeff Ubben, whose ValueAct fund had been selling shares of Valeant this year but still owned nearly 15 million shares of the company as of the middle of 2015. Both Lone Pine Capital and Viking Global, two of the world’s largest hedge funds, which have well over $20 billion in assets each, also held Valeant (VRX) shares.

Of the thousands of stocks in the market, Valeant had the distinction of being held by a large number of hedge funds. Of the 1,000 hedge funds tracked by Symmetric.IO, roughly 12% owned shares of Valeant. In all, 32% of Valeant’s shares were held by hedge funds. As of August, it ranked No. 12 on Goldman’s list of the favorite stocks of hedge fund managers.

Hedge funds pride themselves, and justify their large fees, by saying they do tons of research and find investments off the beaten path. But in the past few years, it seems more and more hedge fund managers own more of the same stocks. And that could be a problem.

“There is some … herd mentality in hedge fund land,” says Jonathan Liggett, a financial advisor who helps clients pick hedge funds. “They share investment philosophies and often the same stocks.”

With Valeant, Liggett says Ackman probably set a trend that other funds followed. Liggett says hedge fund managers often pour over the lists of stocks that are owned by some of the top hedge fund managers, and choose their positions from there. “Ackman certainly attracts followers.”

The copycat behavior may also be related to the growth of the hedge fund industry. As more funds set up shop, there may be fewer novel positions out there. And as more money is invested in hedge funds, even more funds may start to look alike.

Symmetric recently did a study of hedge fund concentration, and it found that, among all hedge funds, portfolio overlap tends to be relatively small. But they also found that “a bunch of really well known funds … have basically the same positions,” says Symmetric’s Sam Abbas. For instance, Lone Pine Management shared four of the top 10 picks of Tiger Global, the hedge fund run by Chase Coleman, who is famous for his early investment in Facebook (FB).

This could be a problem for individuals or pension funds that invest in hedge funds. They could end up not as diversified as they think. What’s more, hedge funds might have trouble justifying their high fees if they are holding the same stocks as a rival.

Such imitative investing behavior could also be a problem for investors in general. When hedge funds pile into the same stock, it tends to makes those stocks, and the market overall, more volatile. It drives up the prices of stocks and tends to make them more susceptible to big swings when bad news happens. That’s what we have seen with Valeant, whose shares have dropped 50% in the past month, as the company faces investigations into its drug pricing policies and, in the past week, allegations that it uses affiliated specialty drug distributors to inflate sales. Valeant denies it has done anything wrong. It is holding a conference call on Monday to address the issues.

But if it turns out that Valeant is a fraud akin to Enron, the so-called smart money that has piled into the stock en masse, will look pretty dumb.

About the Author
By Stephen Gandel
See full bioRight Arrow Button Icon

Latest in Finance

Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025

Most Popular

Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Finance
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam
By Fortune Editors
October 20, 2025
Fortune Secondary Logo
Rankings
  • 100 Best Companies
  • Fortune 500
  • Global 500
  • Fortune 500 Europe
  • Most Powerful Women
  • World's Most Admired Companies
  • See All Rankings
  • Lists Calendar
Sections
  • Finance
  • Fortune Crypto
  • Features
  • Leadership
  • Health
  • Commentary
  • Success
  • Retail
  • Mpw
  • Tech
  • Lifestyle
  • CEO Initiative
  • Asia
  • Politics
  • Conferences
  • Europe
  • Newsletters
  • Personal Finance
  • Environment
  • Magazine
  • Education
Customer Support
  • Frequently Asked Questions
  • Customer Service Portal
  • Privacy Policy
  • Terms Of Use
  • Single Issues For Purchase
  • International Print
Commercial Services
  • Advertising
  • Fortune Brand Studio
  • Fortune Analytics
  • Fortune Conferences
  • Business Development
  • Group Subscriptions
About Us
  • About Us
  • Press Center
  • Work At Fortune
  • Terms And Conditions
  • Site Map
  • About Us
  • Press Center
  • Work At Fortune
  • Terms And Conditions
  • Site Map
  • Facebook icon
  • Twitter icon
  • LinkedIn icon
  • Instagram icon
  • Pinterest icon

Latest in Finance

Teenage boy on laptop
SuccessJobs
Around 22 million teenagers are making their pocket money on video games, online reselling, and in-game platforms like Roblox
By Emma BurleighJune 9, 2026
33 minutes ago
Lockheed, Palantir and Amazon helped fund Trump’s White House ballroom. They also share more than $50 billion in federal contracts
PoliticsWhite House
Lockheed, Palantir and Amazon helped fund Trump’s White House ballroom. They also share more than $50 billion in federal contracts
By Catherina GioinoJune 9, 2026
36 minutes ago
Traders sitting at computers react
InvestingStock
AI stocks are recovering after suddenly tanking last week as oil prices drop more than 3%
By Stan Choe and The Associated PressJune 9, 2026
39 minutes ago
A for sale sign in front a Spanish style house
Real EstateHousing
Home sales are finally recovering and outpacing economists predictions even as mortgage rates remain high
By Alex Veiga and The Associated PressJune 9, 2026
46 minutes ago
Current price of Bitcoin for June 9, 2026
Personal FinanceCryptocurrency
Current price of Bitcoin for June 9, 2026
By Joseph HostetlerJune 9, 2026
2 hours ago
Current price of Ethereum for June 9, 2026
Personal FinanceEthereum
Current price of Ethereum for June 9, 2026
By Joseph HostetlerJune 9, 2026
2 hours ago

Most Popular

Trump, who has repeatedly called climate change fake, is now threatening Brazil with tariffs over the deforestation of the Amazon
Environment
Trump, who has repeatedly called climate change fake, is now threatening Brazil with tariffs over the deforestation of the Amazon
By Sasha RogelbergJune 8, 2026
19 hours ago
Current price of oil as of June 8, 2026
Personal Finance
Current price of oil as of June 8, 2026
By Joseph HostetlerJune 8, 2026
1 day ago
'We didn’t see this coming': Wall Street eats its forecasts as stocks sell off globally on fear of AI bubble ahead of SpaceX IPO
Economy
'We didn’t see this coming': Wall Street eats its forecasts as stocks sell off globally on fear of AI bubble ahead of SpaceX IPO
By Jim EdwardsJune 8, 2026
1 day ago
Gen Zers are arriving at college unable to even read a sentence—professors warn it could lead to a generation of anxious and lonely graduates
Success
Gen Zers are arriving at college unable to even read a sentence—professors warn it could lead to a generation of anxious and lonely graduates
By Preston ForeJune 7, 2026
2 days ago
'The golden years are not golden': Boomers are hoarding most of America's wealth and power because they're terrified of outliving their money
Economy
'The golden years are not golden': Boomers are hoarding most of America's wealth and power because they're terrified of outliving their money
By Nick LichtenbergJune 7, 2026
2 days ago
Current price of silver as of Monday, June 8, 2026
Personal Finance
Current price of silver as of Monday, June 8, 2026
By Joseph HostetlerJune 8, 2026
1 day ago

© 2026 Fortune Media IP Limited. All Rights Reserved. Use of this site constitutes acceptance of our Terms of Use and Privacy Policy | CA Notice at Collection and Privacy Notice | Do Not Sell/Share My Personal Information
FORTUNE is a trademark of Fortune Media IP Limited, registered in the U.S. and other countries. FORTUNE may receive compensation for some links to products and services on this website. Offers may be subject to change without notice.