The productivity of America's work force fell 0.8 percent last year, the worst decline since 1982, the government said yesterday.

It was the second annual productivity slide for the United States, following a 0.7 percent retreat in 1989.

Between 1982 and 1989, productivity gains had averaged 1.6 percent a year. During much of the 1950s and 1960s, average gains in worker output had reached 2.5 percent per year.

Increased productivity, or getting more worker output per hour on the job, is considered vital to strengthening the nation's economic position.

The latest report shows the United States is continuing to lose its competitive edge in international markets and threatens a long-term reduction in living standards, economist David Jones of Aubrey G. Lanston & Co., a New York securities company, said yesterday.

The slide is likely to continue, he said, unless "we sharply improve the quality of our labor force through education, or sharply improve savings and investment in new plants and equipment."

In addition to the data on productivity, the Labor Department report showed that in the final three months of 1990, the nation's businesses trimmed the working hours of employees at an annual rate of 2.7 percent -- the largest falloff since the depths of the 1981-82 recession. It was the second quarterly decline in the number of hours worked, a normal consequence of recession -- as businesses trim payrolls.

While productivity fell for all of 1990, it was about unchanged for the fourth quarter, growing at a small annual rate of 0.1 percent.

In the manufacturing sector, productivity declined at an annual rate of 2.4 percent in the October-December period, the largest drop since 1981. But for all of 1990, manufacturing productivity increased 3.0 percent, reflecting a long-term modernization trend in U.S. factories that began with the 1982 recession.