A "now hiring" sign and job applications are posted outside of the soon-to-be-open Marin Ace Hardware store in San Rafael, Calif. Applications have declined steadily over the past three months and have dropped in four of the past five weeks. The four-week moving average fell 11 percent in 2011, evidence that companies are laying off fewer workers. U.S. private employers added 325,000 jobs in December, according to the ADP National Employment Report jointly developed with Macroeconomic Advisers LLC. Joel Prakken of Macroeconomic Advisers struck a note of caution, telling reporters that the December surge in hiring might have been caused in part by year-end seasonal factors and revisions were possible. Still, economists took a positive view of the data, saying that if Friday's crucial monthly employment report from the Labor Department matches the ADP surge, it could boost optimism that the U.S. recovery, at least, is on solid ground. Economists predict that employers added 150,000 net jobs, which would be an improvement from November's gain of 120,000. The ADP number was a gigantic figure. Even if they're only 50 percent right, the number is still a huge improvement," Landcolt Trading Managing Director Todd Schoenberger told Reuters. An improving labor market has boosted the view the economy wrapped up 2011 on better footing, leaving it well positioned to deal with headwinds from Europe's debt crisis and fiscal tightening at home. Still, a moribund U.S. housing market and persistently high unemployment threaten the recovery. This number is the continuation acceleration of employment began in late summer of 2011, says Joel Prakken, Macroeconomic Advisers, who says GDP numbers is expected to rise in Q4, and a breakdown of the numbers with CNBC's Steve Liesman.