The latest battlefield over equal pay for women will be in U.S. boardrooms, as investors seek shareholder votes on resolutions demanding that nearly a dozen companies reveal their “global median gender pay gaps.”

Arjuna Capital, an investment firm specializing in sustainable and ethical investing, had asked a dozen bank and tech companies to reveal their median pay gaps. So far only Citigroup Inc. has complied, in a Jan. 16 release that showed the median pay for women globally was 71 percent of the median pay for men.