Rosalind Brewer was named the CEO of Sam’s Clubs on Friday, becoming the first woman and first African-American to lead a business unit of Wal-Mart, the world’s largest retailer. Sam’s Club, a bulk sales depot, is the third-largest business unit of Wal-Mart Stores, Inc. out of three divisions.

With the announcement of this news, Brewer joined a tiny sorority of black women who have been tapped to run multi-billion dollar operations with the lauded title of CEO — now totaling two. (Ursula Burns became the first African-American woman in U.S. history to become the CEO of a Fortune 500 company when she took the reigns of the Xerox Corporation in 2009.)

Ms. Brewer had previously run Wal-Mart’s east coast operations as president, leading 550,000 people working in 1,600 stores to generate $100 billion in sales. This division of Wal-Mart is so large, it would garner the 20th position on the Fortune 500 list of America’s largest companies were it a separate business.

By comparison, Sam’s Club is much smaller. With 610 stores and $49 billion in sales for 2011, running Sam’s Club might seem like a demotion for Brewer, but for the lack of black women in the “C-suite” of business leadership. The rarity of black female executives boasting a “C” in their titles — such as chief operations officer, chief financial officer, or CEO — has been chalked up to black women facing a double whammy of racism and sexism in the workplace.

But Brewer’s elevation into this exclusive space might portend even better things for the future of black women advancing, despite the exceptional nature of this occurrence — and for reasons that may come as a big surprise.

According to the 2004 Catalyst report, “Advancing African-American Women in the Workplace,” black women in corporate America — who still face significant obstacles — actually use their cultural differences to their advantage as they battle stereotypes to achieve proper representation in corporate environments.

But Professor Katherine W. Phillips has discovered that certain stereotypes of black women might make them more likely to succeed.

The Paul Calello Professor of Leadership and Ethics at Columbia Business School has made it her mission to study the benefits of workplace diversity for big business. Reflecting on Rosalind Brewer’s ascension to CEO status, Phillips told theGrio, “I think many companies are finding themselves truly confronting a more diverse workforce, and a more diverse customer and supplier base.

“Companies are realizing that they will not survive without a robust strategy for capturing all of the value they can from the people they have available to them,” Phillips said. “People like Ms. Brewer don’t come out of nowhere. Ms. Brewer has been there at Wal-Mart working, learning, and growing into the leader that she has become.”Phillips investigates how firms like Wal-Mart can best capitalize on the value that workplace diversity brings to organizations — and how non-traditional leaders in corporations are perceived. A recent post on the Gender News blog of the Stanford University Institute for Gender Research discusses some of Phillips’ findings regarding how black women are seen in the business world — and the value of a particularly thorny stereotype for their careers.

Dispelling previous assumptions that black women have a harder time making it to the top, “as Phillips’ research got underway she discovered something counterintuitive — in leadership contexts, black women appeared to be helped, not held back, by the angry black woman stereotype,” Gender News reported.

Ironically, just as first lady Michelle Obama has been publicly fuming over feeling continually cast in this role, Professor Phillips has found that the expectation of black women’s decisive assertiveness might help them succeed over typically excluded groups. “People were more open to black women possessing dominant traits than they were to black men possessing them,” making aggressiveness more allowable for these women as a tool for grasping high corporate rungs (Gender News). White women fared the worst in terms of receiving little reward for displaying the direct behaviors that are socially approved of for men.

This social phenomenon seems to be illustrated in the fact that while women of color held only three percent of all board seats of Fortune 500 companies between 2010 and 2011, an astonishing 11.3 percent of the seats held by all women were held by African-American women. Black women represent roughly six percent of the U.S. population.

Could the angry black woman stereotype be behind these impressive numbers? Evidence suggests that, in addition to the hard work, intelligence and tactical planning essential to making it big in business, the presumption that black women are bossy might help them become the boss.

Yet, despite gains made by Brewer, Burns, and the handful of other black women sitting in coveted seats on corporate boards, Phillips urges us to remember that there is much work to be done before African-American women achieve true parity.

“There is still a long way to go, but I hear from some executives that the value of diversity is a foregone conclusion. Now the issue is how to actually capture that value consistently,” Phillips stated about the future of black women in upper levels of management. “I think more companies like Wal-Mart are beginning to appreciate the value of diversity for their companies’ success.”

Yet, “We are still pretty far from significant and lasting changes in the C-suite,” Phillips added.

“It is a long road but there are people and places and situations that you can thrive in,” Phillips said, encouraging black women — and all women — to keep forging ahead. “So I would say to African-Americans and women seeking success in corporate America: don’t give up, keep looking for the right opportunities and don’t be afraid to step out there and try something,” Phillips concluded.

“Prove them wrong, be resilient, and get back up!”