Women and people of color were picked for a majority of open S&P 500 board seats this year for the first time, due in part to pressure from investors to improve gender and racial disparities.

"It's a step in the right direction, for sure, and it's the first time we've gone over 50%," said Julie Daum, who heads the North American board practice for executive recruiter Spencer Stuart, which did the survey. "Boards are looking for people who are younger and with different skill sets, and that does open the boardroom for more women and minorities."

Of 397 independent director slots open in the 2017 proxy season, 36% went to women and 20% to minorities, according to Spencer Stuart, which has tallied boardroom demographics for 30 years. While the tally includes most board seats, it leaves out executives who are also directors of their companies. Combined, women and minorities made up 50.1% of the new board members, compared with 42% last year, the data showed.