The number of American workers in unions declined sharply last year, the Bureau of Labor Statistics reported on Friday, with the percentage slipping to 11.9 percent, the lowest rate in more than 70 years.

The report found that the number of workers in unions fell by 612,000 last year to 14.7 million, an even larger decrease than the overall 417,000 decline in the total number of Americans working.

“It was a very tough year for unionized workers,” said John Schmitt, a senior economist with the Center for Economic and Policy Research in Washington. “We’re seeing declines