Detailed analysis by the task force led by Nicholas Brady found that on October 19 portfolio insurers directly sold almost $2 billion in stocks (nearly 10 percent of that day's volume of trading on the New York Stock Exchange). They also sold S&P 500 index futures equivalent to stocks worth $4 billion, more than 40 percent of externally generated trading in those futures (Brady Commission 1988, p. 36).

Donald MacKenzie, An Engine, Not a Camera, loc. 850