http://www.ft.com/cms/s/0/8f6fbb7e-59ff-11df-acdc-00144feab49a.html
The day after $1,000bn was briefly wiped off the market value of US equities, traders were still trying to work out what caused share prices to plunge and then rebound so dramatically in a matter of minutes.
The conventional wisdom held that an incorrectly typed sell order – one that confused “billions” for “millions”, for example – was the likely culprit.
“The trigger for the sell-off was most likely some kind of errant order, a fat-finger typo, which set off a chain reaction of selling,” said Sang Lee, managing principal at Aite Group. “I would be shocked if that was not the case as the fall in stocks was so sudden and extreme.”
However, despite the persistence of this story, officials were struggling to idenfity a specific cause. “We still don’t know what was the initiating signal for the trading activity we saw on Thursday,” said Jeff Wecker, chief executive officer at Lime Brokerage. “The verdict is still out.”
What was clear was the ferocity of the fall. Just before 2.40pm on Thursday, the S&P 500 index, the US equity market’s benchmark, fell from 1,120. Inside six minutes, it bottomed at 1,065.79, a slide of nearly 5 per cent. By 3.00pm, the index was moving above 1,120, although still down 4 per cent on the day before, settling 3.2 per cent lower by the close.