Women are the primary or co-breadwinner in 6 out of 10 American families. That makes the economic imperative of addressing the wage gap between women and men important, as is every step President Obama can take in that direction.

On Tuesday, Mr. Obama recognized “Equal Pay Day,” the date that symbolizes how far into this year a woman must work on average to catch up with what an average man earned for the previous year, by  signing two executive orders to help reduce the persistent pay disparities.

One order prohibits federal contractors from retaliating against employees for sharing salary information with co-workers. The other directs the Labor Department to adopt regulations requiring federal contractors to report salary data to the agency, including sex and race breakdowns, that can be used to better target government enforcement.

Mr. Obama’s action will apply to about 26 million Americans who work for federal contractors, more than 20 percent of the nation’s work force. Greater transparency could have a significant impact, giving employers incentive to correct unfair pay discrepancies by making it more likely that employees will find out if they are being shortchanged.

Threaded through the political fight over pay fairness is a continuing debate about the size of the pay gap. Mr. Obama and others often cite 77 cents as what women make on average for every $1 earned by men — a figure that critics say is an exaggeration.

In fact, it is a rough, but important, measure of overall workplace inequality. It is not a comparison of what men and women are paid for performing the same or comparable jobs. But, in representing the full-time wages of a working woman against that of a full-time working man, it reflects overt discrimination as well as more nuanced gender-based factors, like the fact that women are disproportionately concentrated in the lowest-paying fields and not well-represented in higher-paying fields. Of course, 77 cents is not the only measure. But there is no doubt that the pay gap is real.

The Pew Research Center last year found that women earned 84 percent of what men earned in its study of the hourly wages of all workers, including those who work part time. Similarly, a 2013 review by the Economic Policy Institute of annual hourly wages for men and women with college degrees, including salaried and hourly workers, found that the men earned on average $33.71 per hour and the women just $25.35 an hour.

Even controlling for hours, occupations, marital status, and other relevant factors, college-educated women earn less than their male counterparts, according to a recent study by the American Association of University Women. And a study issued this month by the Institute for Women’s Policy Research reported that women’s median earnings are lower than men’s in nearly every occupation, including the most common occupations for full-time working women, like elementary- and middle-school teaching and nursing.

Some Republicans have chided Mr. Obama for pointing out the wage gap when the White House has one of its own. Female White House staff members make 88 cents on average for every $1 male employees earn,  the American Enterprise Institute discovered . Jay Carney, the White House spokesman, has awkwardly noted that that is better than the national average and that men and women in the same positions earn the same salary.

But instead of becoming defensive and trying to explain away the discrepancy, Mr. Obama should simply say the White House has to do better and present the lag for what it is: more evidence that the problem persists even in workplaces committed to equal treatment.

On Wednesday,  Senate Republicans blocked consideration of the Paycheck Fairness Act , which would apply the changes ordered by Mr. Obama for federal contractors to the entire American work force as well as make some other important updates to the federal Equal Pay Act. The outcome was entirely predictable. Republicans also stopped the bill in 2010 and 2012. But wage injustice matters to all Americans, regardless of party, and those who stand in the way of fairness do so at their political peril.