Weaker unions, Greater wage inequality - Fact

The NYT reports that the decline in trade union power and membership has played a larger role in fostering increased wage inequality in the United States than is generally thought.

The study, ‘Unions, Norms and the Rise in U.S. Wage Inequality’ published in the American Sociological Review, found that the decline in union power and density since 1973 explained a third of the increase in wage inequality among men since then, and a fifth of the increased inequality among women.
http://economix.blogs.nytimes.com/2011/08/04/labors-decline-and-wage-inequality/?smid=tw-nytimeseconomix&seid=auto

The study concludes that union strength has a bearing on earnings across the whole economy not just in unionised workplaces:

“In the early 1970s, when one in three male workers were organized, unions were often prominent voices for equity, not just for their members, but for all workers,” the two professors wrote. “Union decline marks an erosion of the moral economy and its underlying distributional norms. Wage inequality in the non-union sector increased as a result.”