US STOCKS-Wall St tumbles; S&P below 50-day moving average
* Investors fret over Argentina default fallout
* Exxon, Whole Foods both fall after results
* Jobless claims rise more than expected in latest week; wages rise
* Indexes down: Dow 1.2 pct, S&P 1.5 pct, Nasdaq 1.9 pct (Updates to midday trading)
By Ryan Vlastelica
NEW YORK, July 31 (Reuters) - U.S. stocks slumped in a broad decline on Thursday, with the S&P 500 falling below a key technical level and erasing its gains for the month as concerns mounted over the strength of overseas economies and ongoing tensions with Russia.
The benchmark index, falling in its biggest one-day decline since April 10, moved solidly under its 50-day moving average, a level it has not closed below since April 15, though it has dipped under it since then. The moving average is viewed as a sign of short-term momentum, and selling accelerated after the level was breached.
All ten primary S&P 500 sectors were down on the day, with energy the biggest decliner with a drop of 1.8 percent. Almost 90 percent of stocks traded on the New York Stock Exchange fell, while 82 percent of Nasdaq-listed shares were lower. The CBOE Volatility index rose 20 percent to 15.98, its highest level since April, though well under its historical average of 20.
"We've been extended from the 50-day moving average and are correcting those excesses," said Bruce McCain, chief investment strategist at Key Private Bank in Cleveland, Ohio. "The levels we were at were pretty optimistic given how little clarity we had about global economic growth going forward." Continuación...