"Berkshire Hathaway was built by Warren Buffett to withstand a global economic shock like this one. ": Billionaire investor Bill Ackman bought more than $200 million worth of Berkshire Hathaway stock after the novel coronavirus ravaged stock markets, signaling his confidence in Warren Buffett's conglomerate. "Berkshire Hathaway was built by Warren Buffett to withstand a global economic shock like this one," Ackman said in Pershing Square's 2019 annual report, published this week. The hedge fund boosted its stake in Berkshire by 39% last month using some of the $2.6 billion windfall from its coronavirus hedges, Ackman said in the report.