6 May 2010: Stock prices can go down as well as up. Never in financial history has this adage been more apt than on 6 May 2010. Then, the so-called “Flash Crash” sent shocks waves through global equity markets. The Dow Jones experienced its largest ever intraday point fall, losing $1 trillion of market value in the space of half an hour. History is full of such fat-tailed falls in stocks. Was this just another…