The U.K. recently mandated that large employers reveal gender pay gap data, but U.S. companies are not required to do so, so Citi's report was an instance of radical transparency. In going public with the figures, of course, Citi introduced itself to criticism that tighter-lipped companies shield themselves from. So why make the disclosure? Perhaps most importantly, there was shareholder pressure to do so. Last year, Arjuna Capital convinced Citi —along with Bank of America and Wells Fargo—to reveal pay gap data after arguing for more information on compensation. When Citi released an "adjusted" pay gap that revealed that men and women with the same job title, education, and experience earned roughly the same pay, Arjuna filed a shareholder proposal that Citi report its a median firm-wide gender pay gap in a more straightforward fashion.