Imagine working at a job for years before learning by chance that you have been paid less than a co-worker for the same work. Women, and their households, lose hundreds of thousands of dollars over their lives to a gender wage gap that’s caused by discrimination. These are earnings that could have been used for housing, education and retirement.

We support a legislative fix to this problem proposed by San Francisco Supervisor David Campos. Among other important provisions, Campos’ Equal Pay Ordinance would require employers who do business with San Francisco to report data on pay equity, including a summary of compensation paid to employees identified by sex and race.

Women in California make on average 84 cents to the $1 earned by men. California ranks a dismal 19th in the nation for African American women’s pay; they earn 63.8 cents for each $1 earned by white men. And California’s pay gap is the worst in the nation for Latina workers, who make just 43.6 cents to every $1 earned by white men in this state.

Why is the gender wage gap so wide in California? One answer: Women can’t fight hidden pay discrimination.

The truth is that neither workers nor government agencies have the information they need to detect pay discrimination. Today, in San Francisco, employers who contract with the city have no obligation to reveal whether our tax dollars are being spent on discriminatory pay practices.

Armed with numbers on what women and men are paid by contractors, city officials would be better able to ensure they are doing business with companies that fairly pay and promote all people. Following President Obama’s landmark executive order requiring pay transparency from federal contractors who employ 26 million people across the country, it makes sense for San Francisco, a leader in groundbreaking workers’ rights legislation, to require the same of our city contractors.

Microsoft CEO Satya Nadella may have put it best when he apologized for giving a room full of women at a tech conference some really bad advice: to specifically not ask for raises. Nadella later said: “Any advice that advocates passivity in the face of bias is wrong. Leaders need to act and shape the culture to root out biases and create an environment where everyone can effectively advocate for themselves.”

We encourage the leaders of San Francisco to take action, approve this new legislation, and shape a culture that promotes transparency and the importance of fair pay.

This piece was also written by Rachael Langston, staff attorney for the Legal Aid Society-Employment Law Center.