Data spikes pose problems for risk management

Traders were stunned on May 6 when the Dow Jones Industrial Average fell by nearly 1,000 points before rebounding – its biggest intra-day loss since 1987. This price action was accompanied by a surge in the number of trades and quotes on the New York Stock Exchange (NYSE) – close to 1.2 billion were recorded, compared with a daily average of between 400 million and 600 million.

Regulators and academics are now trying to work out exactly why the Dow moved so far so fast. Blame was initially put o