"It's just a tough market for stock pickers, " says Marc Harris, director of U.S. equity research at RBC Capital Markets.

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The other billionaires, who invested separately from Blavatnik, are Leon Black, Joshua Harris and Marc Rowan--cofounders of New York private equity firm Apollo Global Management.

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Joining the aforementioned group of U.S. deals in the global top 10 were BankUnited and private equity firm Apollo Global Management, run by billionaires Leon Black, Marc Rowan and Joshua Harris.

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