And yet a significant number of men still don't believe it exists.
Sallie Krawcheck, the former Citi CFO who became one of the highest-ranking women on Wall Street, thinks more men in power need to wake up to the realities of the wage gap.
According to the 2018 Money Census report from Ellevest,
a women's investing firm Krawcheck founded, 83% of women said they believe in the gender wage gap, "in which men make more than women for performing the same job." Only 61% of men agreed.
Detractors on both the right and the left have said the wage gap is a myth, concocted from skewed stats that don't account for hours worked and experience earned. In other words: While women on the whole might earn less, women aren't making less than men who do the same jobs.
Much of the gender wage gap can be explained by factors like "occupational segregation" (when work in female-dominated fields is valued less than work in male-dominated fields) and women's traditional roles as unpaid caretakers and caregivers, according to the Pew Research Center.
Ariane Hegewisch, study director at the Institute for Women's Policy Research, believes there's another element to men's disbelief: They don't want to believe they are benefiting from an unequal system — which would imply that they've been rewarded for more than just their own merits.
"You don't want to be the bad guy, so you kind of rationalize it in your head," Hegewisch said. "There are lots of ways of making sense of this for yourself, which doesn't really address the kind of more structural inequalities that I would think we need to fix."
Hegewisch says part of this is men's belief that while some workplaces may be unfair, theirs is not. When confronted with a pay gap between one man and one woman, she said men will often point to a reason other than gender to explain the pay disparity: "she is getting paid less because she is not as good at her job" or "I make more money because I work more hours than she does," or "the man has more qualifications."
Krawcheck predicts more women will leave companies with persistent wage gaps, either to start their own businesses or to work with managers who are aware of the wage gap's effects and actively trying to correct them.
Or, she said, women within these companies may also organize, utilizing the power of women's groups or unions to demand equal pay.
But she's skeptical about the power of unconscious bias training or education focused on convincing men of the wage gap's reality.
"I wish I could say I was hopeful, but we've been educating people and it just doesn't work so I don't know why particularly it would work now," she said. "I think companies will change because women force them to."
She also has a question for the 61% of men who responded "yes" when asked if they believe in the wage gap: "Well, if you believe it's there, why are you not doing something about it?"