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

Exclusive

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

An hour in the Oval Office with President Trump Fortune Editor-in-Chief: Alyson Shontell sat down with President Trump in the Oval Office for an hour. Tariffs, Intel, AI, Boeing, Iran—and the question every CEO eventually has to answer: who's next?

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

Google’s I/O conference showed how the company is being completely rebuilt for AI—for better or for worse
Big TechGoogle
Google’s I/O conference showed how the company is being completely rebuilt for AI—for better or for worse
By Alexei Oreskovic and Sharon GoldmanMay 19, 2026
5 hours ago
Why the 137-year-old developer Hongkong Land is reinventing itself—and trying to broaden its focus beyond its home city
AsiaHong Kong
Why the 137-year-old developer Hongkong Land is reinventing itself—and trying to broaden its focus beyond its home city
By Nicholas GordonMay 19, 2026
6 hours ago
Svenja Gudell, Chief Economist, Indeed
SuccessFortune Workplace Innovation
Indeed chief economist says the sectors most exposed to AI are seeing a big growth in job demand
By Emma BurleighMay 19, 2026
6 hours ago
The 30-year yield hasn’t been this high since the Great Recession. Do the bond vigilantes ride again?
EconomyBonds
The 30-year yield hasn’t been this high since the Great Recession. Do the bond vigilantes ride again?
By Eva RoytburgMay 19, 2026
7 hours ago
traffic
Future of WorkJobs
Goldman Sachs: The U.S. labor market is healthier now than when ChatGPT launched. Yes, really
By Nick LichtenbergMay 19, 2026
9 hours ago
Customer paying for order of cheese in grocery shop.
Personal Financeshopping
Buy now, pay later is the new financial lifeline for lower-income Americans, as consumer loans pile up to $19 trillion
By Tristan BoveMay 19, 2026
10 hours ago

Most Popular

The Bezos family just donated $100 million to help achieve one of Mayor Zohran Mamdani’s top campaign promises
Politics
The Bezos family just donated $100 million to help achieve one of Mayor Zohran Mamdani’s top campaign promises
By Jake AngeloMay 12, 2026
7 days ago
While Trump insisted the Iran war would end ‘soon,’ an account in his name was buying millions in oil, defense, and gold
Economy
While Trump insisted the Iran war would end ‘soon,’ an account in his name was buying millions in oil, defense, and gold
By Eva RoytburgMay 18, 2026
1 day ago
Current price of silver as of Monday, May 18, 2026
Personal Finance
Current price of silver as of Monday, May 18, 2026
By Joseph HostetlerMay 18, 2026
2 days ago
Employers are quietly pausing 401(k) matches again. The last time this happened was the 2008 recession and Covid
Personal Finance
Employers are quietly pausing 401(k) matches again. The last time this happened was the 2008 recession and Covid
By Courtney Vinopal and HR BrewMay 18, 2026
1 day ago
Current price of oil as of May 18, 2026
Personal Finance
Current price of oil as of May 18, 2026
By Joseph HostetlerMay 18, 2026
2 days ago
Current price of oil as of May 19, 2026
Personal Finance
Current price of oil as of May 19, 2026
By Joseph HostetlerMay 19, 2026
14 hours 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.