NEW YORK (MarketWatch) The Dow Jones Industrial Average skidded more than 300 points Thursday in its biggest one-day drop in six months, as a combination of earnings, economic news and a default by Argentina triggered a broad selloff. Investors weighed the implications of robust economic growth and signs of rising wage inflation on Federal Reserve policy ahead of the key monthly jobs report on Friday. The day's losses mean both the S&P 500 and Dow industrials suffered their first monthly decline since January. The S&P 500 SPX -2.00% fell 39.40 points, or 2%, to 1,930.67, its steepest one-day percentage drop since April, and lost 1.5% over July. All 10 main sectors dropped more than 1.5% on Thursday, as the energy and telecom sector stocks lead losses. The Dow Jones Industrial Average DJIA -1.88% dropped 316.99 points, or 1.9%, to 16,563.37, its worst showing on both counts since Feb. 3. It finished the month 1.6% lower and its performance for 2014 turned negative. The Nasdaq Composite COMP -2.09% lost 93.13 points, or 2.1%, to 4,369.77 and fell 0.7% over July. The implied volatility on the S&P 500, as measured by the CBOE Vix index and dubbed "Wall Street's fear gauge", jumped 27% to 17. Kim Caughey Forrest, investment analyst at Fort Pitt Capital, said there was no single reason that should warrant such a selloff, making the drop more difficult to explain. "At the same time, we were surprised to see markets go up in light of all of the uncertainty and geopolitical tensions. Perhaps, investors finally caught up with some of the news," Forrest added.
