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Computers tank the stock market
trades automated chart 3

Most trades today are ordered up by computers, and at speeds measured in milliseconds. The good thing is that this lowers costs. But more automation raises the risk of "flash crashes," in which a mistaken trade starts a chain reaction of robo-selling.

"A program can do something dumb at a much faster rate than a human," says finance and information technology professor Terrence Hendershott of UC-Berkeley.

In 2005, the average time to execute a trade on the New York Stock Exchange was 10 seconds. By 2012, that time dropped to 8/10,000 of a second.

  @Money - Last updated January 28 2013 01:31 PM ET
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