"Perhaps (the) underlying economic performance is accelerating, and even Washington can't screw it up," said Dan Greenhaus, chief global strategist at BTIG.One company that hired last year and would like to add more jobs in 2013 is Arteriocyte, a Cleveland-based stem-cell therapy and medical device company. But CEO Don Brown is concerned about potential cuts in government spending, which he says could erode Arteriocyte's revenue. One such cut is a 2 percent reduction in the reimbursements Medicare gives doctors and hospitals. That reduction was delayed by the budget deal reached this week. If the reimbursement cut is imposed later this year, it would lower revenue for the hospitals and surgeons that buy Arteriocyte's advanced products. "Our entire customer base is unsure about what their reimbursement landscape is going to be," Brown said. The Obama administration's health care reform law also imposed a 2.2 percent sales tax on medical devices. Brown estimates that will cost his company $400,000. He had hoped the tax would be eliminated as part of a fiscal cliff agreement. Arteriocyte hired 10 workers last year and now employs 76. The new hires included research scientists, two marketing specialists and a sales representative. Brown hopes to make five to 10 additional hires this year, but he might be unable to do so if the Medicare cut takes effect. Despite last month's hiring gains, Friday's report pointed to some weakness in the job market. For example, the number of unemployed actually rose 164,000 to 12.2 million. About 192,000 people entered the work force last month, but most did not find jobs. The unemployment numbers come from a government survey of households. The number of jobs added comes from a separate survey of businesses. A broader category that includes not only the unemployed but also part-time workers who want full-time jobs and people who have given up looking for work was unchanged in December at 22.7 million.