Like many Americans, I’ve been wary of labor unions.

Full-time union stagehands at Carnegie Hall earning more than $400,000 a year? A union hailing its defense of a New York teacher who smelled of alcohol and passed out in class, with even the principal unable to rouse her? A police union in New York City that has a tantrum and goes on virtual strike?

More broadly, I disdained unions as bringing corruption, nepotism and rigid work rules to the labor market, impeding the economic growth that ultimately makes a country strong.

I was wrong.

The abuses are real. But, as unions wane in American life, it’s also increasingly clear that they were doing a lot of good in sustaining middle class life — especially the private-sector unions that are now dwindling.

Most studies suggest that about one-fifth of the increase in economic inequality in America among men in recent decades is the result of the decline in unions. It may be more: A study in the American Sociological Review, using the broadest methodology, estimates that the decline of unions may account for one-third of the rise of inequality among men.