After almost five months of investigations led by Gregg E. Berman,[7][8] the U.S. Securities and Exchange Commission (SEC) and the Commodity Futures Trading Commission (CFTC) issued a joint report dated September 30, 2010 and titled "Findings Regarding the Market Events of May 6, 2010" identifying the sequence of events leading to the Flash Crash.[9]
The joint report "portrayed a market so fragmented and fragile that a single large trade could send stocks into a sudden spiral,"[10] and detailed how a large mutual fund firm selling an unusually large number of E-Mini S&P 500 contracts first exhausted available buyers, and then how high-frequency traders (HFT) started aggressively selling, accelerating the effect of the mutual fund's selling and contributing to the sharp price declines that day.[10][11][12][13][14][15][16][17]
The SEC and CFTC joint report itself says that "May 6 started as an unusually turbulent day for the markets" and that by the early afternoon "broadly negative market sentiment was already affecting an increase in the price volatility of some individual securities." At 2:32 pm (EDT), against a "backdrop of unusually high volatility and thinning liquidity" that day, "a large fundamental trader (a mutual fund complex) initiated a sell program to sell a total of 75,000 E-Mini S&P 500 contracts (valued at approximately $4.1 billion) as a hedge to an existing equity position." The report says that this was an unusually large position and that the computer algorithm the trader used to trade the position was set to "target an execution rate set to 9% of the trading volume calculated over the previous minute, but without regard to price or time."[9]
As the large seller's trades were executed in the futures market, buyers included high-frequency trading firms – trading firms that specialize in high-speed trading and rarely hold on to any given position for very long – and within minutes these high-frequency trading firms also started aggressively selling the long futures positions they first accumulated mainly from the mutual fund.[10] The Wall Street Journal quoted the joint report, "'HFTs [then] began to quickly buy and then resell contracts to each other—generating a 'hot-potato' volume effect as the same positions were passed rapidly back and forth.'"[10] The combined sales by the large seller and high-frequency firms quickly drove "the E-mini price down 3% in just four minutes."[10]
From the SEC/CFTC report itself:
The combined selling pressure from the Sell Algorithm, HFTs and other traders drove the price of the E-Mini S&P 500 down approximately 3% in just four minutes from the beginning of 2:41 pm through the end of 2:44 pm. During this same time cross-market arbitrageurs who did buy the E-Mini S&P 500, simultaneously sold equivalent amounts in the equities markets, driving the price of SPY (an exchange-traded fund which represents the S&P 500 index) also down approximately 3%.
Still lacking sufficient demand from fundamental buyers or cross-market arbitrageurs, HFTs began to quickly buy and then resell contracts to each other – generating a “hot-potato” volume effect as the same positions were rapidly passed back and forth. Between 2:45:13 and 2:45:27, HFTs traded over 27,000 contracts, which accounted for about 49 percent of the total trading volume, while buying only about 200 additional contracts net.[9]
As prices in the futures market fell, there was a spillover into the equities markets. The computer systems used by most high-frequency trading firms to keep track of market activity decided to pause trading, and those firms then scaled back their trading or withdrew from the markets altogether.[10][11][12][13]
The New York Times then noted "Automatic computerized traders on the stock market shut down as they detected the sharp rise in buying and selling."[12] As computerized high frequency traders exited the stock market, the resulting lack of liquidity "...caused shares of some prominent companies like Procter & Gamble and Accenture to trade down as low as a penny or as high as $100,000."[12] These extreme prices also resulted from "market internalizers,"[18][19][20] firms that usually trade with customer orders from their own inventory instead of sending those orders to exchanges, "routing 'most, if not all,' retail orders to the public markets – a flood of unusual selling pressure that sucked up more dwindling liquidity."[13]
While some firms exited the market, firms that remained in the market exacerbated price declines because they "'escalated their aggressive selling' during the downdraft."[10] High-frequency firms during the crisis, like other firms, were net sellers, contributing to the crash.
The joint report said prices stopped falling when, "At 2:45:28 pm, trading on the E-Mini was paused for five seconds when the Chicago Mercantile Exchange ('CME') Stop Logic Functionality was triggered in order to prevent a cascade of further price declines. In that short period of time, sell-side pressure in the E-Mini was partly alleviated and buy-side interest increased. When trading resumed at 2:45:33 pm, prices stabilized and shortly thereafter, the E-Mini began to recover, followed by the SPY."[9] Or as the New York Times reported, "The rout continued until an automatic stabilizer on the futures exchange cut in and paused trading for five seconds, after which the markets recovered."
The joint report noted that after a short while, as market participants had "time to react and verify the integrity of their data and systems, buy-side and sell-side interest returned and an orderly price discovery process began to function," and that by 3:00 pm (EDT), most stocks "had reverted back to trading at prices reflecting true consensus values" and the Flash Crash was over.
