Even with overwhelming evidence to the contrary, some people believe the gender wage gap is a myth.

On Thursday, a new study by the Economic Policy Institute (EPI) provides (even more) evidence of the gender pay gap.

One of the key findings from the study is that unionization helps women get closer to equal pay.

"Working women in unions are paid 89 cents for every dollar paid to unionized working men; nonunionized working women are paid 82 cents for every dollar paid to nonunionized working men."

The reason? Union contracts offer “more transparency on how wages are set, less inequality,” Elise Gould, one of the study's authors, told Rewire.

Previous research backs up this finding. A 2014 study by Center for Economic and Policy Research found unionization raises wages for women, on average, by 12.9 percent more. According to the Institute for Women's Policy Research (IWPR), women in unions are also more likely to remain in their occupation, and in general, union membership is linked to "higher wages, increased access to and participation in employer-provided pension plans, and subsidization or complete coverage of health insurance premium by one’s employer."

While women's union membership is increasing, women in leadership position in unions is still disproportionately low, even when women make up the majority of a union, reports IWPR.

Overall, By EPI's measurement of data from the U.S. Bureau of Labor Statistics, a “typical, or median” woman working full-time is paid 80 cents for every dollar a man is paid. The authors note that this number is only based on "differential pay for equivalent work." The authors explained:

"[T]his simple adjustment misses all of the potential differences in opportunities for men and women that affect and constrain the choices they make before they ever bargain with an employer over a wage."

According to the report, factors influencing the width of the wage gap include race or ethnicity, education level, occupation, and motherhood. Notable takeaways: Black and Hispanic women are affected the most, hit with "the double penalty" of both racial and gender pay gaps, and "the motherhood wage penalty," a form of discrimination against mothers, is still alive and well.

The cost, though, for any woman over the course of her professional life is shockingly high. According to the National Women's Law Center, on average, American women will make $430,480 less than men over 40 years of work."

[h/t The Cut]