The 8-hour workday. Social Security. Even slowing the spread of Ebola. Unions have been improving society for a long time.

Now we know that unions—particularly those with collective bargaining rights—also close the gender pay gap. New research from the economists Barbara Biasi and Heather Sarsons highlight a striking example. (Shout out to the Economic Policy Institute’s Ben Zipperer for spotlighting this.)

Remember back in 2011 when then-Governor Scott Walker stripped collective bargaining rights from nearly all of Wisconsin’s public employees? Shortly after, women public school teachers began making less income than men teachers with the same credentials—and the gender pay gap is now growing rapidly.

The data is profound and unequivocal: Since losing collective bargaining, women have been less likely to negotiate salaries and less likely to succeed in getting pay raises at schools run by a male principal or superintendent.

In other words, unions are a powerful tool in the feminist movement’s toolbox.

We already knew that unions helped address gender pay disparities. A 2017 Economic Policy Institute study found that women in unions were paid 94 cents, on average, for every dollar paid to unionized men. That’s not exactly pay equality. But it’s much better than the 78 cents non-union women were paid, on average, for every non-union men’s dollar in wages.

But now we can add closing the gender pay gap to the growing list of good things collective bargaining does for our communities.

Like when Los Angeles’s teachers won better wages and benefits but also the hiring of more school nurses, more green space at every school, support for immigrant families, a stop to random police searches at schools, and more.

Or like when Oregon’s largest unions won higher wages, paid sick days, better retirement security, and nondiscrimination protections for most full-time workers statewide.

Despite what folks like Scott Walker say, unions give a voice and rights to the people who do the work, teach our kids, care for us, and hold our society together. They’re essential to democracy.

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Photo by Richard Hurd.