* Facebook slumps in premarket after earnings
* Initial jobless claims, Chicago PMI data on tap
* Futures: Dow +5 pts, S&P off 1.4 pts, Nasdaq off 9.75 pts
NEW YORK, Jan 31 (Reuters) - U.S. stock index futures edged lower on Thursday ahead of data on the labor market and a slew of corporate earnings reports.
* Facebook Inc shares dropped 6.7 percent to $29.14 in premarket trading. The company doubled its mobile advertising revenue in the fourth quarter but that growth trailed some of Wall Street's most aggressive estimates.
* Qualcomm Inc gained 6 percent to $67.35 in premarket trading after the world's leading supplier of chips for cellphones beat analysts' expectations for quarterly profit and revenue and raised its financial targets for 2013.
* Investors will look to weekly initial jobless claims data at 8:30 a.m. ET (1330 GMT) for clues on the health of the labor market ahead of the payrolls report on Friday. Economists in a Reuters survey forecast a total of 350,000 new filings compared with 330,000 in the prior week.
* Also at 8:30 a.m. (1330 GMT), the Commerce Department will release December personal income and spending data; economists expect a 0.8 percent rise in income and a 0.3 percent increase in spending.
* ConocoPhillips reported a drop in quarterly profit as oil and gas prices weakened and output from the third-largest U.S. oil and gas producer remained steady compared with a year ago, though it anticipated a decline in the first quarter.
* Later in the session at 9:45 a.m. (1445 GMT), the Institute for Supply Management Chicago releases January index of manufacturing activity. Economists in a Reuters survey forecast a reading of 50.5 compared with 50.0 in December.
* S&P 500 futures fell 1.4 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 rose 5 points, and Nasdaq 100 futures lost 9.75 points.
* The S&P 500 is up 5.3 percent for the month, as legislators in Washington temporarily sidestepped a "fiscal cliff" of automatic tax increases and spending cuts that could have derailed the economic recovery, and amid improving economic data and better-than-expected corporate earnings.
* But the benchmark index has stalled recently, hovering near the 1,500 mark over the past four sessions as investors look for more catalysts to justify further gains.
* Thomson Reuters data through Wednesday morning shows that of the 192 companies in the S&P 500 that have reported earnings this season, 68.8 percent have exceeded expectations, a higher proportion than over the past four quarters and above the average since 1994.
* Overall, S&P 500 fourth-quarter earnings are forecast to have risen 3.8 percent. That's above the 1.9 percent forecast from the start of the earnings season, but well below a 9.9 percent fourth-quarter earnings growth forecast on Oct. 1, the data showed.
* European shares fell as investors digested mixed earnings reports, with a warning from AstraZeneca knocking its shares while Ericsson surged after fourth-quarter results.
* Asian shares fell slightly after rallying to multi-month highs, and more for some Southeast Asian markets, while the U.S. Federal Reserve's pledge to retain its stimulus policy undermined the dollar.