In 2011, a hundred thousand people poured into the streets of Madison, Wisconsin to oppose newly elected Republican governor Scott Walker’s severe budget repair bill, which imposed devastating austerity and cratered the state’s public sector unions. Approaching a decade since the legislation’s passage, we’re now able to assess the grim legacy of Walker’s anti-worker crusade, which reduced total union membership in Wisconsin by 31 percent between 2013 and 2018.

One aspect of this legacy is the emergence of a gender pay gap among teachers. A new working paper by Barbara Biasi and Heather Sarsons conducted for the National Bureau of Economic Research, titled “Flexible Wages, Bargaining, and the Gender Gap,” finds that there is now a discrepancy in male and female teachers’ pay in Wisconsin, whereas before Walker’s legislation there was none.

Walker’s aggressive budget repair bill was one of the most belligerent assaults on unions in living memory. There is a special significance to the fact that it occurred in Wisconsin, long a bastion of public sector unionism and the first state to allow teachers to unionize in 1959. The legislation was so brutal that it earned Walker a reputation as “one of the most anti-union, hard-line conservative governors in America” and “perhaps the most anti-worker politician in the whole country.”

One of the major features of Walker’s legislation was its requirement that public sector unions hold annual elections to decide whether or not each union should continue to exist. This put unions in front of the firing squad every year, perpetually vulnerable to union-busting campaigns. While teachers’ unions have tended to be more resilient than other public sector unions in Wisconsin, there was indeed “a great wave of teachers’ union decertification” following the implementation of Walker’s bill.

Additionally, Walker’s legislation severely limited the scope of what remaining public sector unions could collectively bargain over. Whereas before, union contracts would extend uniformly to every teacher according to fixed schedules based on seniority and level of education, Wisconsin has now seen the introduction of “flexible wages,” meaning that each individual teacher is responsible for negotiating his or her own salary and benefits once union contracts expire. Even in districts that have retained a formal schedule structure, Walker’s legislation introduces a degree of individual negotiation.

So how did these changes result in a gender pay gap? Well, as Biasi and Sarsons observe, there is already a large body of scholarship indicating that women are reluctant to negotiate for raises relative to their male counterparts. Their own surveys found that women were 31 percent more likely to report that they feel uncomfortable negotiating for higher pay. The gender composition of management played a decisive role in whether women actually overcame their hesitations and opted to negotiate individually for better wages anyway. Biasi and Sarsons concluded that the gender pay gap is largest when schools are run by male principals or when districts are run by male superintendents.

The researchers also control for other potential factors, and find that the gap “is not explained by gender differences in teacher ability or job mobility, and is unlikely to be driven by a higher demand for men in certain schools.” In other words, it really does come down to who feels comfortable asking for a raise from whom, elevating the importance of interpersonal power dynamics which are heavily informed by gender difference. The research indicates that this is not an issue when all workers bargain together through their union, only when they’re compelled to negotiate as individuals.

Some might suggest that increasing the proportion of women in management could solve the problem. But however desirable that might be, the authors’ findings suggest it would only do so if we were willing to outright ban male bosses from managing women in all sectors throughout the nation. Instead, the most practical solution to this problem is to restore workers’ ability to bargain collectively.

Furthermore, the gender pay gap has not been the only consequence of Walker’s anti-union legislation for teachers. Wisconsin teachers on average have seen their benefits and salaries decline and their class sizes grow since 2011. Even if the gender pay gap were to be reduced by some means other than restoring full collective bargaining rights, the average situation of Wisconsin’s majority-female education workforce would still be worse than before the implementation of anti-union legislation. For the sake of women teachers, then, building and empowering unions is a priority.

Biasi and Sarsons’s findings illustrate that unions can act like a shield against some of the most injurious effects of sexism (and other unequal power dynamics and forms of prejudice, for that matter). When the shield falls away, women workers are especially vulnerable. Because the majority of women are workers, it follows that the cause of feminism can’t be meaningfully advanced without a firm commitment to workers’ rights and organized class struggle. That requires strengthening unions, in Wisconsin and beyond.