Hedge funds entered 2020 on a bit of a roll. The Preqin All-Strategies Hedge Fund benchmark delivered an 11.45% return in 2019 - only the second time the industry has registered double-digit returns since the beginning of 2014.

The pressure was on to repeat the performance in 2020. But COVID-19 hit, and all bets were off. Billionaires and hedge funds with billions in assets have spent the first part of the year trimming or completely exiting positions.

As we've said in looking at billionaires' top stock picks, it's both interesting and constructive to know what the "smart money" is doing. That's because they boast rich resources and deep connections to insiders that can give them insights into stock picks that most other people simply don't have. It can be equally instructive to look at what they're unloading, and why.

Here are 25 stocks that billionaires have been selling so far in 2020. Many of those sales were stocks most likely to be affected by the virus: airlines, hotels, retailers, restaurants, casinos and other businesses that can't make money without people physically visiting their establishments or utilizing their services. In some cases, however, the "smart money" prudently took profits on holdings that were working quite well for them. And once in a while, you'll find that some billionaires are ditching what other institutional investors covet.

Allergan

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David Tepper, the billionaire owner of the Carolina Panthers and the manager of hedge fund Appaloosa Management, sold 46% of Botox maker Allergan during the first quarter, reducing its weighting in the Appaloosa portfolio from 6.2% at the end of December to 3.8% at the end of March, but it remained the firm's seventh-largest holding.

Tepper wasn't the only smart-money manager to sell off a large chunk of AGN. John Paulson's Paulson & Co. shed roughly 2.1 million shares, or 77% of its stake, during the first quarter.

Of course, Allergan shares don't exist anymore. On May 8, biopharmaceutical firm AbbVie (ABBV) closed its $62 billion deal to buy AGN after clearing U.S. antitrust hurdles, creating a combined entity that should generate $50 billion in annual revenues.

"The new AbbVie will be a well-diversified leader in many important therapeutic categories, with both on-market and pipeline assets, and our financial strength will allow us to continue to invest in innovative science and continue to serve unmet medical needs of patients that rely upon us," AbbVie CEO Richard Gonzalez said upon the deal closing. "I am proud of both organizations and look forward to the opportunities ahead."

What's notable about the deal is that Allergan shareholders received $120.30 in cash and 0.8660 shares of ABBV for every share held. So it appears that Tepper and Paulson alike held onto some of their Allergan stock to roll into AbbVie. We'll see if they maintained those stakes when they report their second-quarter 13Fs, which should happen in August.

Amazon.com

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Hong Kong real estate billionaire Peter Woo is worth an estimated $13.3 billion. On May 25, Wharf Holdings - a 73%-owned subsidiary of Wheelock Properties, a holding company controlled by the billionaire - announced it had sold 223,452 shares of Amazon.com (AMZN, $2,545.02).

Wharf's announcement stated that it had sold Amazon shares between Aug. 5, 2019, and May 22, 2020, at an average price of $1,975