The car industry is no bastion of female empowerment, so it was groundbreaking to see General Motors appoint Mary Barra as CEO in December. She is the first woman not just to run the company, but to run any global carmaker. But on the heels of that historic news came something sadly less surprising: her current pay package is less than half of what was given to the man who just vacated the role. True, as the company has pointed out, she may well get more when shareholders vote later this year on her long-term compensation package, but her base salary and short-term package are lower than the man’s before her. And she is in no way the only female executive to be paid less than the men around them.

After President Obama mentioned the gender wage gap in his State of the Union by citing the average figure that women make seventy-seven cents for every dollar a man makes, some conservatives have once again pushed back at that figure, and with it, the notion that there is a discrimination-created wage gap. True, that seventy-seven cents figure includes many different factors, including wage penalties women may accrue for taking time off to take care of kids, for instance, not just employers simply paying women less. But to see discrimination at work, all you have to do is look to the top.

Barra’s pay package is lower not because she’s a newbie who might have taken years off from her career to care for family members. Barra has logged thirty-three straight years with the company, most recently serving as senior vice president of global product development. Her predecessor, Don Akerson, on the other hand, came to the job with zero years of experience in a car company, although he had sat on GM’s board since 2009. In response to a question about Barra’s lower base pay, a company spokesperson told me Akerson got more because he was also named the chairman and because he had been a CEO before—just not at any car companies. Barra, in dedicating her career to the carmaker, hadn’t gotten the chance yet.

Women who reach the top can’t be accused of lacking ambition. Not surprisingly, the few who make it—women still represent less than 15 percent of CEOs at the country’s largest companies—are extraordinarily ambitious, more so than their male peers. They haven’t opted into lower-paid jobs—they’re at the very top. They haven’t decided or been forced to put family before career, or at least not so much that it stopped them from reaching the pinnacle of their organizations.

Yet the highest-paid female executives at S&P 500 companies make 18 percent less than men in the same position. The gender wage gap among CEOs, in fact, is 69 percent, a bigger gap than that average for everyone. Barra isn’t the only one. Heather Bresch, the CEO of the pharmaceutical company Mylan, makes 33 percent less than what the average chief pharma executive can expect. Denise Morrison, CEO of Campbell Soup, makes 24 percent less than the average in the food industry.

What can explain this gap? These women have climbed to the top of their companies. They have worked hard and reached high. Why do they deserve to be paid less than the men who did the same? I can’t see any other explanation for it than discrimination. And there’s good reason to think discrimination hurts other women’s pay: When it examined multiple factors that might explain the disparity in pay, the Government Accountability Office couldn’t explain a 20 percent gap between women’s and men’s earnings, saying that it’s likely discrimination is at fault.

Pay gap skeptics often cite different work histories, women ending up in lower-paying jobs, and the fact that young women see a smaller gap as reasons to doubt the 77 percent figure. But it’s worth noting that even these factors represent discrimination, although it is on a societal level, not the employer level. The work women are more likely to perform—think care work, teaching, service jobs—pays a lot less than what men tend to do. In fact, male-dominated fields pay nearly $150 more each week than female-dominated ones. This is not only thanks to society’s telling women they aren’t the stuff of engineers but a devaluing of the work women do. Women are the default caretakers in a society that still doesn’t realize that most families feature two working parents or a single one, but our policies present working parents with impossible choices: Go back to work too quickly after the arrival of your new child or suffer financial hardship while on unpaid leave? Risk your job or your pay to take a day off to care for a sick kid or find someone else to care for him? Pay for incredibly expensive childcare or have a parent leave work and stay at home? No wonder women feel pressure to interrupt their careers to care for children—someone often has to. Women even get more college degrees yet earn less than men with the same educational credentials.

The gender wage gap is complicated, and throwing around the 77 percent figure can sometimes mask the various factors that go into it. But it’s impossible to rule out discrimination as at least one, if not the biggest, cause of it when the women who reach the top are still valued less.