trader’s faulty sell order for 16 billion—rather than 16 million—Procter & Gamble shares. Another theory blamed the iconoclastic trader Nassim Taleb, whose 2007 bestselling book The Black Swan popularized the historical importance of rare, high-impact, difficult-to-predict events. On the afternoon of May 6th, a Taleb-advised hedge fund, Universa, placed an influentially hefty bet