The motivation isn’t entirely altruistic. Morgan Stanley research shows that 86 percent of millennials, who represent more than 75 million potential clients, are interested in environmental, social and governance — or ESG — investing, which surged by a third in the U.S. during the two years ending Dec. 31, 2015, to $8.7 trillion, according to data from US SIF: The Forum for Sustainable and Responsible Investment. Within this group, assets that consider diversity grew 22 percent to $707 billion.

Diversity also makes money. Studies increasingly show a critical mass of female directors improves return on equity, profits and decision making. Even so, five S&P 500 companies and at least 700 in the Russell 3000 still have all-male boards. Canada and Europe, where many nations have quotas, surpassed the U.S. in 2014.

Shareholders filed 35 diversity proposals at American companies this year, five times as many as in 2011, according to ISS Corporate Solutions’ Voting Analytics database. Only eight went to a vote; most were withdrawn when the company agreed to engage privately with investors.

The big three didn’t vote in favor of all eight, according to data from Fund Votes. They also didn’t back a dozen proposals seeking equal pay for women. The firms say they want diversity but don’t always support the resolutions, especially if they’re speaking with management and see progress.

BlackRock did oppose management’s proposed directors at five of the companies. The world’s largest money manager, with almost $6 trillion under management, has four women on its own board, or 24 percent, slightly above the U.S. average. Twenty-six percent of its senior leaders are women. Chairman and CEO Laurence D. Fink has said he wants gender parity.

“More than 50 percent of household wealth is managed by women,” Fink said at the Bloomberg Global Business Forum in September. “If I’m going to be a mirror of my clients, we are going to need more women.”

Diversity is also a priority at Vanguard, which manages $3.4 trillion of equities and owns significant stakes in some companies, including 16 percent of Hudson Pacific.

“We expect boards to focus on it as well, and their demonstration of meaningful progress over time will inform our engagement voting,” CEO F. William McNabb III wrote in an Aug. 31 letter to companies worldwide.

These public voices matter even more now. Republican legislators and members of business lobbying groups are seeking to raise the bar for filing proposals to 1 percent of a company’s outstanding capital from just $2,000 now. This would eliminate Pax and other small activist investors.

Even a majority vote doesn’t guarantee change, though. Six months after 63 percent of shareholders at Cognex Corp. supported a diversity measure, the Massachusetts-based maker of machine-vision equipment still hasn’t added any women to its nine-man board. Cognex didn’t respond to requests for comment.