Stocks dipped slightly Thursday, but the Standard & Poor's 500 still logged its best January since 1997.
The Standard and Poor's 500 fell 4 points to 1,498, gaining 5.1 percent for the month. It was the index's strongest month since October 2011.
The Dow Jones industrial average fell 50 points to 13,860. It's up 5.8 percent this month.
The Nasdaq composite fell a fraction to 3,142. It's up 4.1 percent this month.
Advancing stocks on the New York Stock Exchange outpaced declining ones. Volume of 3.9 billion shares was above average.
A mixed bag of economic data gave more reasons for investors to be cautious ahead of the all-important jobs report due on Friday.
Investors expect a pullback in equities after the recent gains, though they have bought on dips over the past four weeks. The largest daily decline on the S&P 500 so far in 2013 was Wednesday's 0.39 percent drop after data showed the economy contracted in the fourth quarter of 2012.
On Friday, the government is due to release figures on January's non-farm payrolls, which are expected to show employers added 160,000 jobs in January after a rise of 155,000 in December.
"It's the calm before the potential storm. The uncertainty about tomorrow's numbers comes from that fact that we had a decent ADP report but the weekly claims were not so great," said Randy Frederick, managing director of active trading and derivatives for Charles Schwab in Austin, Texas.
"We could see an overly sensitive market to a bad number tomorrow, given that we've been up without a major correction, and that makes the market sensitive to the downside."
Data on Thursday showed a slight rise in weekly jobless claims and incomes growing at the best pace since 2004, underscoring how fragile the economic recovery still was.
Friday will also bring reports on consumer confidence, U.S. manufacturing, construction spending and car sales.
Qualcomm gained 4.4 percent to $66.32 as the top boost to the Nasdaq Composite after the world's leading supplier of chips for cellphones beat analysts' expectations for quarterly profit and revenue and raised its targets for the year.
Facebook shares fell 0.8 percent to $31.01 after falling as low as $28.74 a day after the social network company said it doubled its mobile advertising revenue in the fourth quarter. However, growth trailed some of Wall Street's most aggressive estimates.
The S&P 500 has advanced in January after legislators in Washington temporarily sidestepped a "fiscal cliff" of automatic tax increases and spending cuts that could have derailed the recovery. Better-than-expected corporate earnings have added to the gains.
UPS shares lost 2.1 percent to $79.50 after reporting fourth-quarter earnings that were below analysts' estimates on Thursday and forecasting weaker-than-expected profit for 2013.
Constellation Brands shares tumbled 16.4 percent to $32.72 after the U.S. Justice Department moved to stop Anheuser-Busch InBev from buying the half of Mexican brewer Grupo Modelo that it does not already own. Constellation would have distributed Corona beer in the United States if the transaction had been approved.
Tank barge operator Kirby Corp added 6.3 percent to $70.67 and transportation company Ryder Systems climbed 4.8 percent to $56.84 after posting quarterly results.
Thomson Reuters data through Thursday morning shows that of the 231 companies in the S&P 500 that have reported earnings this season, 69.3 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 3.7 percent. That's above a 1.9 percent forecast at the start of the earnings season but well below a 9.9 percent profit growth forecast on October 1, the data showed.
Slot machine maker WMS Industries surged 51.7 percent to $24.84 after the company agreed to be acquired by Scientific Games for $26 per share in cash. Scientific Games jumped 5 percent to $9.38.