Flock of Swans

On 6 May 2o1o, the Flash Crash hit at 2:45pm and the stock market lost 1000 points in only a few minutes, spurred by frantic sell orders from automated trading systems.Because we haven't seen anything as radical as the Flash Crash before or since, it's been assumed that this sort of thing is fairly rare.A new study by Neil Johnson and his cohorts at Florida University shows that flash crashes— "black swan events"— occur more than once a day on average.  18,520 times between 2006 and 2011.They...