There’s an insidious undercurrent of thought in the American corporate world: Mothers just don’t make good workers. Their brains get hormonally addled when they have children, and they take their eyes off the prize and onto their newborns. Most people aren’t dumb enough to say this out loud, but occasionally someone—like the billionaire investor Paul Tudor Jones—slips up. In 2013, he said:

As soon as that baby’s lips touched that girl’s bosom, forget it. Every single investment idea, every desire to understand what’s going to make this go up or go down is going to be overwhelmed by the most beautiful experience which a man will never share about a mode of connection between that mother and that baby.

Though Tudor Jones walked that statement back with a mealy mouthed explanation—he said he was speaking “off the cuff”—a similar assumption often lurks behind public discussions of “opting out”: Mothers are leaving the workforce because they just can’t hack it. But the truth is women are rational economic actors, just like men are. That’s underscored by new research showing that women who get paid maternity leave are less likely to leave their jobs.

In the New York Times, Claire Cain Miller points out that our country’s lack of family-friendly policies compared with other wealthy nations has caused the U.S. to fall behind in women’s labor force participation. According to a study by economists Francine D. Blau and Lawrence M. Kahn, the U.S. had the highest labor force participation among women in 1990. By 2010, we’d fallen to 17th. This is due in no small part to the fact that we are the only wealthy nation that does not have any federal paid maternity leave, and that our child care system is comparatively terrible.

That means that more American women are knocked out of the workforce when they have biological children: not because of some magical mind-meld between mother and child, but because having a baby is exhausting and requires a measure of physical recovery. A woman has to take a break when she has a baby, whether it’s paid or not, while a male partner can get by without time off unless he’s paid to take it. And when mothers are the primary caretakers from day one, that sets a precedent: If a family can’t afford child care, it’s generally the mother who will leave her job to pick up the slack. This phenomenon is backed up by census data: Wealthier first-time moms who can afford child care are more likely to work full time until their last months of pregnancy, they’re more likely to benefit from paid leave, and they’re more likely to return to their jobs once their babies are born.

The fact that poor women don’t have access to paid leave isn’t just contributing to the pay gap between men and women; it’s also widening the wealth gap between poor mothers and their wealthier counterparts. As Cain Miller points out, in California, where paid family leave exists, low-income moms nearly doubled their maternity leaves since paid leave was instituted. But after the maternity leaves end, mothers of small children in California both work more and earn more than they previously did. If the rest of the country would just follow suit, we could begin to stamp out gendered biological stereotypes about what mothers can achieve—and we’d make everybody more productive.