As union membership has declined in the United States, wages have remained largely stagnant for the last three decades.
In some industries -- like construction -- they've actually fallen.
About 14% of construction workers were union members last year, down from 22% 25 years earlier. Meanwhile, real wages for construction workers fell from $780 per week in 1986, to $746 in 2011.
Union workers earn about $361 more per week than their non-union counterparts.
Major unions: Laborers' International Union of North America; United Steelworkers of America; United Brotherhood of Carpenters and Joiners of America
NEXT: Transportation and warehousing workers