Accident or?

NYT, 'High-Speed Trading Glitch Costs Investors Billions,' by Nelson Schwartz and Louise Story: 'The glitch that sent markets tumbling Thursday was years in the making, driven by the rise of computers that transformed stock trading more in the last 20 years than in the previous 200 ... The old system of floor traders matching buyers and sellers has been replaced by machines that process trades automatically, speeding the flow of buy and sell orders but also sometimes facilitating the kind of unexplained volatility that roiled markets Thursday.'



Forbes, 'Fat Fingers Cause Panics,' by Vahan Janjigian: 'Why the market plunged so much and so fast in the middle of the afternoon isn't entirely clear. Some blame an erroneous quote on Procter & Gamble (PG), saying it caused panic selling across the board. Others say the selloff was caused by a trading error on the Nasdaq. This so-called fat-finger error occurred when a trader accidentally entered an order to sell a billion shares rather than a million shares. Still others blame the rioting in Greece for the selloff. That rioting was widely broadcast on trading floors. These reasons might explain the extent of today's selloff only if investors were already extremely nervous to begin with, which I believe they were. ... They were happy to see their stocks go up, but they were also prepared to sell at the first hint of trouble. That trouble came this afternoon, so they sold with a vengeance.'