In other cases, a change in the pay culture has been pushed from the outside. At Mills & Reeve, a British law firm whose audit determined it was paying women an average of 32 percent less than men, a major impetus has come from big clients that have started to request more female representation among the firm’s attorneys.

“It’s increasingly something we’re asked for as part of tenders and pitches, to give details of our diversity,” said Claire Clarke, a managing partner.

Some efforts predate the new rules, but have come into focus because of the requirements. The British bank Barclays, for example, has sought to hire, and retain, more senior female executives by offering a new 12-week “internship” targeted at experienced women who are coming off a career break and introducing greater flexibility in existing jobs.

Supporters of the British regulations acknowledge that transparency alone won’t solve the problem. But without it, companies and regulators in countries seeking to enforce equal pay laws would have scant evidence that a gap existed — and face less pressure to address it. Jake Rosenfeld and Patrick Denice, sociologists at Washington University, found in a study that salary transparency raised wages, in part because “even being cognizant of gender pay disparity” helped change norms.

Such is the case in Iceland. The country has gone further than any other, becoming the first to require employers to submit to external audits to prove they are paying women on a par with men. The thinking was that unless equal pay laws were applied more forcefully, the imbalance might never close.

Iceland’s government has vowed to completely close the nation’s gender pay gap by 2022, after women walked out of their jobs en masse in protest on a chilly afternoon in October 2016.