Among private industries, the union membership rate was the highest in transportation and public utilities in 2001, at 23.5 percent. Of all wage and salary workers in private industry, 9.0 percent were union members in 2001.
The construction and manufacturing industries also had higher-than-average unionization rates, at 18.4 percent and 14.6 percent, respectively. The industry with the lowest unionization rate in 2001 was agriculture—1.6 percent. Other private industries with below-average unionization rates were finance, insurance, and real estate; wholesale and retail trade; and services.
In contrast to private industry, 37.4 percent of government workers were union members in 2001.
Bureau of Labor Statistics, U.S. Department of Labor, The Economics Daily, Union membership in private industry, 2001 at https://www.bls.gov/opub/ted/2002/jan/wk2/art05.htm (visited September 27, 2022).