Sluggish hiring last month closed out a year of weak employment gains that have frustrated job seekers even as layoffs and unemployment have also been low. Employers added 50,000 jobs in December, nearly unchanged from a downwardly revised figure of 56,000 in November, the Labor Department said Friday. The unemployment rate slipped to 4.4%, its first decline since June, from 4.5% in November, a figure also revised lower. The data suggests that businesses are reluctant to add workers even as economic growth has picked up.