* Philly Fed, leading economic indicators miss estimates
* UnitedHealth profit falls, shares drop
* Initial claims roughly in-line with expectations
* Indexes off: Dow 0.29 pct, S&P 0.34 pct, Nasdaq 0.51 pct
By Chuck Mikolajczak
NEW YORK, April 18 (Reuters) - U.S. stocks dipped on Thursday after a batch of weaker-than-expected economic data triggered more concerns about the global economy and put the S&P 500 on key a technical support level.
The Philadelphia Federal Reserve Bank said its business activity index dropped to 1.3, from 2.0 the month before, shy of economists' expectations for 3.0.
In addition, the Conference Board said its Leading Economic Index dropped 0.1 percent, below the expected 0.1 percent increase and the first drop in seven months.
The data represent the latest in a string of economic reports that have pointed to a weakening in the global economy, including disappointing growth in China, retail sales data last week and payrolls data earlier in April.
The number of Americans filing new claims for unemployment benefits increased 4,000 to a seasonally adjusted 352,000 last week, slightly above the 350,000 estimate, which could further temper fears of a major setback in the labor market recovery.
Equities have been whipsawed in the past three sessions, with a 1 percent move in either direction in the S&P 500 each day this week, the first such streak of volatility for the index since the start of February.
Worries about global demand have sparked selloffs in commodities, which in turn have led to weakness in equities. However, some equity investors continue to use any dips as a buying opportunity.
Investors also grappled with the pace of earnings season starting to pick up.
"You've got a weak market today based on the weak economic data," said Ken Polcari, Director of the NYSE floor division at O'Neil Securities in New York.
"And people are starting to be a little more sensitive to what those earnings actually say - not only what those earnings are because they are already here, but what they are saying about the future."
UnitedHealth Group Inc lost 4 percent to $59.57 as the biggest drag on the Dow after the largest U.S. health insurer said its first-quarter profit had fallen.
But fellow Dow component Verizon Communications Inc advanced 3.2 percent to $51.13 after the telephone company posted a higher than expected quarterly profit, driven by strength in its wireless business.
Morgan Stanley (Xetra: 885836 - news) reported a stronger-than-expected first-quarter profit of $958 million, compared with a year-earlier loss of $119 million, as its wealth management business grew, but shares lost 3.2 percent to $20.79.
The Dow Jones industrial average dropped 42.28 points, or 0.29 percent, to 14,576.31. The Standard & Poor's 500 Index dipped 5.30 points, or 0.34 percent, to 1,546.71. The Nasdaq Composite Index lost 16.19 points, or 0.51 percent, to 3,188.48.
In another bearish signal, the S&P 500 briefly broke below its 50-day moving average of around 1,543, while the small-cap Russell 2000 index has been trading below its 50-day moving average since Monday.
Volume has been heavier on selling days, as many investors have been anticipating a pullback for some time after the strong run to start the year and are quick to book profits.
"They rode it all the way up on no volume but when they decide they want to take some money off the table, they are going to be a little more aggressive," said Polcari.
Earnings are expected to be soft this quarter, but most companies are forecast to beat earnings estimates that have been reduced by analysts.
S&P 500 earnings are now expected to have risen 1.9 percent in the first quarter, up from the 1.5 percent estimate at the start of the month, based on actual results from 82 companies and estimates for the rest, according to Thomson Reuters data through Thursday morning.
Of the 82 companies that have reported earnings, 72 percent have topped analyst expectations but only 43.9 percent have beaten revenue forecasts.