Union Density

Union density is calculated as total U.S. union membership divided by employment. We report both industry level and aggregate union density numbers. We use membership and employment averages by decade (1910-1919, 1920-1929, and so forth). The last period is 2000 to 2015.  Employment data are drawn from  the decennial Census from 1910 to 2000. Beginning in 2001, we use the yearly American Community Survey (ACS).  Union membership numbers are collected by us, detailed in the union membership section.


See Methodological Appendix for further details.