The American economy added 304,000 new jobs last month, while the nation's unemployment rate rose from 3.9 percent to 4 percent, according to new data published by the U.S. Bureau of Labor Statistics. Job gains occurred primarily in leisure and hospitality, construction, health care, and transportation and warehousing, according to the Bureau. The unemployment rate also rose between November and December, from 3.7 percent to 3.9 percent.