U.S. job openings fell to the lowest level in more than five years, another sign that the American labor market remains sluggish. The Labor Department reported Tuesday that vacancies fell to 6.5 million in December — from 6.9 million in November and the lowest since September 2020. Layoffs rose slightly. The number of people quitting their jobs — which shows confidence in their prospects — was basically unchanged at 3.2 million.