Although many studies show a positive relationship between extent of unionization and union members' wages, some analysts suggest that this relationship could reflect a concentration of labor organization in industries with potentially high wage gains, rather than unions' efficacy in raising...

Two well-documented empirical findings are that unionized employees typically receive substantially higher compensation than their non-union counterparts and that union representation in the United States has declined over time. Some observers have hypothesized a causal link between these two...