By Ryan Vlastelica

NEW YORK (Reuters) - Stock index futures were lower on Friday as investors took profit following a recent rally, though they remained on track to close out a seventh straight month of gains.

Equities have been strong this year, with the S&P 500 jumping 3.6 percent in May and 16 percent in the year to date, taking it repeatedly to record highs. Over the past seven months, the index has gained 17 percent.

The gains have largely come on supportive monetary policies from central banks around the world, which has helped the markets avoid the Wall Street adage of "sell in May, go away," which refers to a historical trend of weakness in the month. The S&P fell 6.3 percent in May 2012.

Despite the gains, shares have been volatile over the past few weeks on uncertainty over when the stimulus programs will be scaled back or stopped.

"We're way behind average in terms of volatility this year, and that's starting to creep back into the market," said Art Hogan, managing director at Lazard Capital Markets in New York. "But for the moment it appears the near-term move is for some profit taking after a strong run."

Investors are also looking ahead to the latest data, with April personal income and spending data scheduled for release at 8:30 a.m. EDT (1230 GMT); both are seen rising 0.1 percent, compared with the 0.2 percent gain last month.

May Chicago PMI data, a read on manufacturing, is due at 9:45 a.m. EDT (1345 GMT) and is seen coming in at 50, above 49 last month. At 9:55 a.m. (1355 GMT), the final May Thomson Reuters/University of Michigan read on consumer sentiment is seen holding steady at 83.7.

"While it wouldn't be unusual to see a dip in markets after the gains we've had, the tone could change if the data comes in to the upside," said Hogan. "PMI could especially be a catalyst as manufacturing hasn't recently been an area of support."

S&P 500 futures fell 8.1 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures slid 79 points and Nasdaq 100 futures lost 16.5 points.

For the week, the Dow is up 0.1 percent, the S&P is up 0.3 percent and the Nasdaq is up 0.9 percent.

Semiconductor stocks will be in focus a day after Avago Technologies Ltd forecast third-quarter revenue that was largely above expectations, citing a revival of demand from a large customer.

On the downside, Palo Alto Networks plunged 12.5 percent to $47.60 in premarket trading after giving an outlook that was below expectations.

The Food and Drug Administration late Thursday refused approval to Endo Health Solutions Inc's injectable testosterone drug, asking for a better risk management plan.

One of the biggest minority shareholders in Clearwire Corp on Thursday urged the wireless company to recommend against Sprint Nextel Corp's buyout offer after Dish Network Corp made a counter bid.

U.S. stocks closed modestly higher on Thursday following data on the labor market and GDP. While the numbers were weaker than expected, they soothed concerns about the Fed scaling back its stimulus measures any time soon.

(Editing by Bernadette Baum)