The number of workers applying for unemployment benefits in the United States dropped sharply last week to a level not seen in 52 years, adding to signs of a tightening labor market and suggesting businesses were reluctant to let go of workers. First-time filings for unemployment insurance—a proxy for layoffs—came in at 184,000 for the week ending Dec. 4, the Labor Department said in a report (pdf). That’s a drop of 43,000 from the prior week’s revised level of 227,000 and well-below consensus forecasts of 215,000. This is the lowest level for initial jobless filings since the week of Sept. 6, 1969, when 182,000 claims were filed. The data dovetails with other labor market data showing American workers quit their jobs at a near-record pace in October while job openings rebounded to near-record highs, adding to signs of labor market tightness. “This is truly a ‘Great Back’ jobless claims reading,” Bankrate Senior …