Major Stock Selloffs Just Aren't What They Used to Be
Stocks Head for Worst Slump Since August
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Volatility is back -- at least by this year’s standards. The 0.8 percent retreat in the S&P 500 Index just after noon in New York is what passes for a two-sigma drop in the benchmark gauge.
For calendar year 2016, it would’ve taken a 1.6 percent decline to qualify as a two-sigma move. In 2015, a sell-off of 2 percent was needed for such a change in the standard deviation of the benchmark index.