“When you’re the ONLY in the room, you have an opportunity to differentiate yourself”-Ursula Burns

When Ursula Burns quietly shut off the light to her office as Xerox CEO at the end of 2016, her departure also cast a light on a sad statistic: There are currently zero African-American women running Fortune 500 companies. Burns’ appointment to the top job in 2009 had been hailed as a milestone. Suddenly it looked more like an anomaly.

Her story is in many ways perfect for a pioneering figure. She grew up poor on New York’s Lower East Side, the middle child of a single mother who washed and ironed clothes for money. Burns’ strength in math got her scholarships and a summer internship at Xerox. The company invested in her early and often. She made it all the way to the corner office

This is where Burns rips the needle from the record. “I’m not sure why people are so shocked that someone who had been doing something for eight or 10 years would want to move on,” she says. She’s also not sure why people would be

First, she laments the state of schools and communities that fail to care for low-income children of color and graduate them ready to work. It takes 20 years of education to grow an entry-level employee, or more if they are going to have a specialty that employers really want—like STEM or professional services. Even with black women graduating from college in record numbers, “not enough are coming out of the education system to get them all the way through to the C-suite,” says Burns. And the black women who do make it often end up in support positions rather than the operational roles that lead to CEO jobs. “HR isn’t going to get you there,” she says. “Communications and the arts aren’t going to get you there.” The juice lies with people who are close to the product and the money. “So, now look at the numbers of women we have now. Unless you’re bringing people in from Mars, it’s going to be a while.

Burns says there are plenty of things corporate America can and should be doing to make sure that the black women currently in the pipeline have a chance to succeed on their own terms. But the lessons of her experience are worth remembering.

“Thirty years ago, when I started working—literally the chances of me making it were worse than minuscule,” she says. “We should be saying ‘hooray’ to the people of Xerox,” she says. “We should be giving them a medal.”

When Fortune’s editors sat down to compile this year’s ranking of the 50 Most Powerful Women in Business, another alarming statistic jumped out: One. That’s the number of African-American women on this year’s list, represented by Ann-Marie Campbell, No. 18, Home Depot’s EVP for U.S. stores. (Former Sam’s Club CEO Rosalind Brewer, recently named COO of Starbucks, is On Our Radar.) The lack of black women in top jobs stands out all the more because of recent gains by women in the C-suite. When this year’s Fortune 500 was published in June, there were a record 32 women in CEO jobs, up from 21 in 2016. (The number has since dipped to 29.)

At long last, it appears that cracks are beginning to form in the glass ceiling. But for African–American women a barrier remains in place. Call it the Black Ceiling.

Apart from the elements cited by Burns, that ceiling is composed of several complex socioeconomic factors. Black women are at a disadvantage in trying to bridge the familiarity gap with white men in positions of power, because in the words of talent management research firm Catalyst, they are “double outsiders”: They’re neither white, nor men. As a result they’re often shut out from the informal networks that help other people find jobs, mentors, and sponsors.

The research, which is drawn from a large group of survey respondents Catalyst has tracked for years, also shows that black women often grow demoralized in the workplace. They report environments that they feel continually overlook their credentials, diminish their accomplishments, and pile on cultural slights—about their hair, appearance, even their parenting skills. And they often have fraught relationships with white women, who tend to take the lead on issues of women and diversity. “This is what we call an ‘emotional tax,’” says Dnika J. Travis, an executive and researcher at the Catalyst Research Center for Corporate Practice. “The burden of being on guard all the time affects our lives in really negative ways.”

This small, stressed, and hardworking cohort has extraordinary potential to lead. “One of the things that I think is remarkable about black women is that even with all of the headwinds that we face in terms of advancing ourselves, there is this incredible appetite for learning and preparing ourselves for leadership,” says Susan Reid, Morgan Stanley’s global head of diversity and inclusion. “So many of us grew up in families where we saw women who exhibited real leadership at an early age—like in mine, where my mother was the head of the household.” The gap between that appetite and the opportunities presented cause real frustration and pain. “That gap is what we’re trying to solve for.”

While there are no one-size-fits-all solutions, there are plenty of people stepping up to the challenge in interesting ways.

Burns and other senior leaders say that fostering relationships between senior managers and young black women is a crucial step that almost never happens. “There’s no natural place for these people to get together,” says Burns of potential sponsors and ambitious young people. “These places have to be created. There is no natural pathway for connection; it’s not going to happen just walking down the hall.”

Adds Burns: “And most young people don’t know what they want to do or be. They just know they want to be me, or whoever they’re talking to.”

According to Deloitte and the Alliance for Board Diversity, women and minorities occupied about 31% of the board seats of Fortune 500 companies in 2016—up from 26.7% in 2012. And while 19 black women gained seats on Fortune 500 boards last year, boards remain nearly 80% male. But, insists Rogers, this is not solely a numbers game. “Just getting on the board isn’t enough,” he says.

Other young black women are intent on pushing for change from the inside. One is Katrina Jones of Accenture, who recently took a lead role at the firm in global inclusion and diversity that has her working on initiatives in the U.S., the U.K., and South Africa. She brings a kind of determination to her role that typical job screenings and assessments might not reveal. Jones, 38, grew up in an affluent white suburb of Austin, but her parents grew up in rural Mississippi. “My father literally grew up picking cotton,” says Jones. “I’m dedicated to increasing the number of black women at the firm because I believe in equity,” she says. “What’s a good word for a ‘group of black women?’ ” she muses aloud. “Let’s call that a victory”

While we wait for the next black female CEO, Ursula Burns plans to stay busy. She sits on a variety of boards, including Exxon Mobil, American Express, Nestlé, and the Ford Foundation. “I can be helpful, I’m still relevant,” she says. And she plans to devote much of her energy to education. “I’m not kidding about the pipeline,” she says. “All of these corporate efforts [at STEM education] are amazing, but clearly it’s not enough.”

When asked about how she’d grade her time at Xerox, she begins by talking about disruption in technology and the quest to “add value” to the world, to employees, to shareholders.

Then she falls silent. “I love Xerox,” she says eventually. “I think I did a good job.”

A version of this article appears in the Oct. 1, 2017 issue of Fortune with the headline “The Black Ceiling.”