The number of African American chief executives among the largest public U.S. companies — already a tiny group — is shrinking by one. American Express on Wednesday announced the retirement of its longtime CEO, Kenneth I. Chenault, and when he leaves the credit card issuer's corner office on Feb. 1, only two black chief executives will remain at the helm of companies in the S&P 500 index. That number has fallen in recent years despite a steady drumbeat of attention to the need for more diversity in corporate America.

One of the two remaining CEOs in that index of major public companies is Merck CEO Kenneth Frazier, who gained recent attention for being first among a wave of corporate chiefs to depart President Trump's advisory panels following his remarks in August about protests in Charlottesville. The other, according to the Executive Leadership Council, an organization focused on black leaders, is Arnold W. Donald, chief executive of Carnival cruise lines. (The S&P lists counts 503 chief executives in total because a few companies have co-CEOs.) The Fortune 500 list, which ranks companies by revenue, now includes just three: Frazier, J.C. Penney CEO Marvin Ellison and Roger W. Ferguson Jr., who leads the money manager TIAA.

Just a few years ago, that number was even higher — if still small. McDonald's was helmed by CEO Don Thompson until early 2015, and former Xerox CEO Ursula Burns stepped down after that company split into two earlier this year. “It's disappointing,” said Ron Parker, CEO of the leadership council, in an interview. “When we have so few and we lose one, we all feel we are not making progress.”

Chenault, who major American Express shareholder Warren Buffett called “the gold standard for corporate leadership and the bench mark that I measure others against,” had a 16-year run atop the credit card issuer, navigating the aftermath of Sept. 11, the financial crisis and a recent turnaround effort. Though the company has faced hurdles in recent years as competitors picked off customers, he was known for expanding the company's customer base and being a mentor to other leaders. “He was the dean of CEOs,” said Parker, saying Chenault had been the “architect” of his organization's CEO Academy, a program for developing next-generation African American leaders.

The smaller numbers come at a time when diversity has been a hot-button topic in Corporate America, with companies talking more and more about adding women to leadership roles and improving the number of minorities and women in engineering and technology jobs. But some worry the heavy focus on those issues — while important — could be crowding out broader discussions about the makeup of the executive suite. “Teams that are more diverse, racially, actually make more money too,” said Lawrence James, a partner at the leadership consultancy RHR International. “The financial arguments are there, but people aren't paying attention.”

In Trump's White House, a plum appointment for CEOs has become a reputation risk. Parker and James cited several reasons progress may have slowed, from systemic problems of education and inequality to the relationship building challenges that black managers face in workplaces that are not inclusive and predominantly white. “Black culture and white culture are different,” said James, making it less appealing for black executives to engage in after-work activities where many relationships are built.

The CEO has also become even more of the public face of many companies, expected to manage a Twitter account and apologize on CNBC when something goes wrong. “When you have publicly traded companies, one of the things the board wrestles with is, 'Do we feel comfortable with a female or a person of color representing our enterprise?' " Parker said. “I think it was no different than when our 44th president was in his role.”

Parker and James also cited getting more black directors on corporate boards, where just 5.6 percent of board seats on Fortune 500 companies were held by black men and only 2.2 percent by black women in 2017, according to a leadership council analysis. More minority or women directors, Parker said, should propel more of them to help rising black executives early in their careers get the wide-ranging experience they need, as he says AmEx's board did for Chenault and former Xerox CEO Anne Mulcahy did for Burns.

It could also help keep complacency from setting in, when boards name one or two minority executives in the top ranks but then seem to feel they've done their job. Says Parker: “The one-and-done syndrome is very much alive in Corporate America.”

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