In this case, though, a new study bolsters the strong implication of that graph: Declining union membership is actually responsible for a significant part of the growth in income inequality. The (paywalled) study, by sociologists Bruce Western of Harvard and Jake Rosenfeld of the University of Washington, uses some terrifically frightening statistics to make this case.
Western explains that:
"Most researchers studying wage inequality have focused on the effects of educational stratification—pay differences based on level of education—and have generally under-emphasized the impact of unions."
Some excerpts from the study, which is in the American Sociological Review 76(4), omitting all the stuff about decomposition and reweighting and so on:
- We argue that unions helped institutionalize norms of equity, reducing the dispersion of nonunion wages in highly unionized regions and industries. Accounting for unions' effect on union and nonunion wages suggests that the decline of organized labor explains a fifth to a third of the growth in inequality—an effect comparable to the growing stratification of wages by education. (513)
- [D]eunionization's effects on inequality are only half as large as education's effects for women, but union and education effects are equally large for men. (528)
- [We argue] that unions not only equalize union members' wages, they also equalize the nonunion wage distribution by threatening union organization and buttressing norms for fair pay. We found strong evidence that unionization rates in detailed industries for geographic regions are positively associated with wage equality among nonunion workers. (532)
- The decline of U.S. labor and the associated increase in wage inequality signaled the deterioration of the labor market as a political institution. Workers became less connected to each other in their organizational lives and less connected in their economic fortunes. (533)
In other words, when Republicans and their corporate masters go after unions, they're not just coming for non-union workers next, they're already doing it. And when they tell you that unions are just looking out for their own members at your expense, they're saying something that contradicts the facts.