Irrational exuberance has been exorcised from Wall Street, for now. A raucous week ended with the stock market having booked its most brutal decline in about two years. Both the Dow Jones Industrial Average DJIA, +1.38% and the S&P 500 index SPX, +1.49% registered their worst weekly declines, about 5.2% each, since January 2016, while the Nasdaq Composite Index COMP, +1.44% posted its worst week since February 2016, with a 5.1% tumble. To recap, the Dow posted two 1,000-point drops during the week’s five trading sessions, something it has never done in its history, and has notched three percentage declines of at least 2% in six sessions after having gone more than 100 without a single decline of more than 1%. Add to that the fact that a product that gauge’s volatility on Wall Street, the Cboe Volatility Index VIX, -10.50% , saw on Monday its largest percentage rise in its roughly quarter-of-a-century history, obliterating a period of eerily persistent placidity in the market. By Thursday, the S&P 500 and the Dow had slipped into correction territory, typically defined as a retreat of at least 10% from a recent peak. via