In the United States, the gender pay gap has women earning approximately $0.80 for every dollar their male counterparts are taking home. When people become parents, the gap widens even more with moms earning $0.71 per fathers’ dollars.

Now, a recent report from the United States Census Bureau shines some light on how the pay gap and, particularly, the parental pay gap can be equalized.

“This shows that the birth of a child is really when the gender earnings gap really grows,” Danielle H. Sandler, a senior economist at the Census Bureau and an author of the paper, tells The New York Times.

And while the findings have something to do with the timing of when women have children, the takeaways can help us address the gender pay gap on a larger scale: According to the Census Bureau’s research using the Social Security Administration Detail Earnings Records, women who have their first baby before the age of 25 or after the age of 35 ultimately close the salary gap with fathers.

The theory as to why this is comes back to the disproportionate amount of time that mothers spend on housework and child care. (Even if both partners work full-time.) When it feels like something’s got to give, women’s careers often take the hit. Notably, the gap is widest among women who had higher earnings before becoming mothers, which the researchers suggest is because these women have more income to lose.

“A woman who takes off some time or slows down or shifts into a smaller firm will be losing out on a really high income, which her husband appears to be getting,” Harvard economist Claudia Goldin tells The New York Times, explaining this has been corroborated by her own research.

As for why women who have children before 25 or after 35 don’t feel as much of a hit, the researchers suggest it’s because they are either not yet established or are already established in their careers.

So, what can we do for those millions of women who have babies in their late twenties or early thirties? Provide better support in the form of paid family leave, workplace re-entry assistance and subsidized child care, researchers say.

Pointing to the paradoxical effects of family leave in Scandinavia—where there is still a sizable gender pay gap—Sandler says a moderate-length leave for both mothers and fathers appears to be the answer, based on findings from economists.

“It seems like there could be a middle ground where you’re given enough leave where you don’t have to quit your employment,” Sandler says. “But not so much time that you have the incentive to be out of the labor force for a long time.”

We’re seeing policies move in this direction around the country—from the grassroots efforts of independent business to the new laws that require employers offer paid leave.

Now, with more research from a level as high up as the Census Bureau showing what’s at stake when we don’t create policies that support families, hopefully the momentum will build even more. Because what’s good for moms is good for everyone.

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