Black Presence On U.S. Boards Shrinks

But things are changing, as bigger institutional investors like pension funds that invest with hedge funds press for more diversity, he said.

Women Make Gains

The decline in black representation stands in contrast to the gains, albeit modest, made by other under-represented groups over the same period, including women, Latinos and Asians.

Some public sector pension fund leaders, including New York City Comptroller Scott Stringer and officials of California Public Employees' Retirement System, have argued for years that boardrooms should more diverse. They have cited studies showing diversity can help companies' financial performance.

The continuing lack of diversity is a reason Stringer has urged companies to make it easier for small investors to run director candidates, a change known as "proxy access," Stringer said in an interview.

"If boards don't move toward diversity themselves, then proxy access enables shareholders to do this for them," he said.

Change at boardrooms may be slow because companies do not have many chances to bring in fresh faces, with the average director staying on an S&P 500 board for 8.5 years, according to Spencer Stuart, a rate that has been roughly stable for the past five years.

Nor is there a strong outlook for increased black representation. Only about 7 percent of newly-named directors at S&P 500 companies this year have been black, the same as in 2014, the only other year in which such data is available, according to Institutional Shareholder Services.

Headhunters said that companies try to achieve many of their priorities, including diversity, with each new appointment, but are bound to fail to meet all of them given new demands.

For instance, Julie Daum, head of Spencer Stuart's North American board practice, said the more recent demand for directors with experience in areas like cybersecurity, means that "boards have many things they need to accomplish with each addition."

The drive for some forms of diversity, such as adding women to boards, can hold back gains for other groups, said Ronald Parker, president of The Executive Leadership Council, which advocates for the promotion of black leaders. Also, senior African-American executives may not have as much experience in particular areas.

Those trends mean companies need to look harder and "move beyond their normal circles to find talent" who could serve as board members, he said.

After Ben Carson

An example of how the various pressures on boards can play out is the case of Ben Carson, an African-American and retired neurosurgeon who's also running for U.S. president.

To focus on his presidential campaign, earlier this year Carson quit the boards of food company Kellogg Co. and retailer Costco Wholesale Corp., where he had served since the 1990s. Since then, each company named two new directors each, all of whom are white, including one woman each.

Costco named two directors who have experience in communications - Maggie Wilderotter, executive chairman of Frontier Communications, and John Stanton, a wireless industry veteran who was CEO of Western Wireless Corp. Costco Chairman Jeff Brotman said both of the directors were tapped before Carson stepped down. While he declined to discuss the selections in detail, he said via e-mail that the company has and is "taking steps to recruit under-represented minorities to our Board."

Kellogg named directors with international experience in consumer goods - Carolyn Tastad, group president of Procter & Gamble North America, and Noel Wallace, president of Colgate-Palmolive Latin America.

Kellogg Chairman and CEO John Bryant said in an e-mailed statement that the company has "a very diverse board with African American, Hispanic and International representation." The company's 14-member board does include six women. One of them is also the board's only African-American, La June Montgomery Tabron.