The Bureau of Labor Statistics reports that union membership rates have fallen off sharply in the past year, from 11.8 percent of the workforce to 11.3 percent.
This is the lowest level since the 1930s, BLS finds.
In terms of head counts, union membership has fallen by 400,000 workers to 14.4 million, the Associated Press reports.
Hardest hit? Teachers unions, according to the report.
Labor union membership peaked in the 1950s, with about one-third of all workers in the United States claiming affiliation. But unions have faced a backlash lately, as cash-strapped states face financial woes, exacerbated by pension promises. And unions also have lost power.
Just last week, the U.S. Court of Appeals in Chicago reversed a lower court ruling that would have favored unions in Wisconsin. The issue in brief: Gov. Scott Walker signed legislation in 2011 restricting collective bargaining rights of some public unions in the state. A lower court ruled that provision was unconstitutional. On Jan. 18, the federal court upheld the law.