According to the U.S. Department of Labor’s Bureau of Labor Statistics (BLS):

“In 2008, union members accounted for 12.4 percent of employed wage

and salary workers, up from 12.1 percent a year earlier… The number of workers belonging to a union rose by 428,000 to 16.1 million. In 1983, the first year for which comparable union data are available, the union membership rate was 20.1 percent, and there were 17.7 million union workers.”

The BLS also reported that “[g]overnment workers were nearly five times more likely to belong to a union than were private sector employees”, the percentage of unionization in those two sectors being 36.8% and 7.6%, respectively.

The most highly unionized state in 2008 was

New York at 24.9% and the lowest was North Carolina at 3.5%.