The world's most powerful economies are increasingly alarmed by declining birthrates, and theories about why abound. Elon Musk suggests society is "teaching a fear of pregnancy." Policymakers in France apparently believe young people have simply forgotten to procreate—so much so that they sent reminder letters to 29-year-olds.
Other explanations are more mundane: raising children costs too much, or would-be parents worry the planet can't support more people.
Now, a working paper by Claudia Goldin, the Nobel Prize-winning economic historian at Harvard University, offers a different theory: perhaps highly educated, career-driven women are reluctant to have children because they fear sacrificing their autonomy to partners who won't share the load of raising them.
"Women who undertake greater investments in themselves will be more likely to have children if they can reap the financial and personal rewards from their education while raising their children," Goldin writes. "In the absence of that assurance, they will be more likely either not to have children or not to undertake the initial investment in themselves."
She adds: "The more that men can credibly signal they will be dependable 'dads' and not disappointing 'duds,' the more investment in women's education and careers, and the higher will be the birthrate in the face of greater female agency."
A Neat Theory—And an Easy Target
The theory is elegant, which makes it vulnerable. Critics point out that birthrates have continued falling even as household labor has become more equitably divided: Bureau of Labor Statistics data shows men's hours on household activities rose slightly over the past decade while women's fell slightly—yet birthrates kept declining. Others question inconsistencies in the underlying data, or ask what "dependability" in a dad even means.
Goldin doesn't claim to have all the answers. "When women did not have any choice, [having children] is what they did," she tells Fortune. "But now they are given a choice." Men have one too, she notes—the choice of how to prove they're a dad rather than a dud. The problem? "We don't really know the answer [to] what sort of commitment mechanisms [men] have."
Perhaps attuned to the dynamic through her research, Goldin says she can spot the telltale signs among her own students: "I can pretty much tell who the good dads are. There's no question—they are the individuals who are clearly going to share and engage in what I would call couple equity."
"Couple equity doesn't mean equality—it doesn't mean you're doing exactly the same things—but it does mean that each of them has decided they're willing to give up a certain amount of income and prestige to raise a child or two, or three together."
Nothing New Under the Sun
Whatever one makes of Goldin's methodology (and the historian welcomes critique), the research is making waves. Google searches for her name have jumped 400% over the past year, and birth rates are climbing the political agenda—President Trump has even suggested he'll be remembered as the "fertilization president," thanks to policies like expanded IVF access.
But the trends behind Goldin's formula aren't new. Women have been investing in education at rising rates for half a century. The BLS found that among recent high school graduates aged 16 to 24 in 2024, 69.5% of women were enrolled in college versus 55.4% of men. Fifty years earlier, Census data show women made up just 45.87% of college students aged 14 to 24.
Beyond personal fulfillment, there's growing economic necessity: a 2020 Brookings study found that without women's earnings, middle-income households would have seen virtually no income growth between 1979 and 2018.
Myra Strober, labor economist and Professor Emerita at Stanford's School of Education, offers a simpler and broader explanation drawn from the same half-century of data: the *need* for children has shifted from the household to society at large.
"Historically, people had children because they needed them," Strober tells Fortune. "In an agricultural economy, you needed children to do the work. As agriculture became less important to our economy, people stopped needing children the way they did before.
"And people had lots of children because infant mortality was high. You couldn't be assured your children would live to adulthood, so you'd better have plenty to help around the farm. Once agriculture declined and infant mortality plummeted, people didn't need children in the way they once did."
Strober founded Stanford's famous "Women and Work" course (later renamed "Work and Family"), where she met student Abby Davisson, now an entrepreneur and consultant. The pair co-authored *Money and Love* in 2023, now required reading at Stanford's Graduate School of Business.
At the book's end, they examine how public policy trickles down into household decisions—"yet we have not changed our policies around work expectations or cultural norms," Davisson tells Fortune. "It's much easier to change policy than culture."
"There's a cultural conversation piece here that's tricky. Even with the best policies—if expectations for parents don't change, if the cost of raising children doesn't change—I don't see how we'll see different behavior at the individual level. It's not just this one piece of policy."
"We should be thinking about the economy as a whole and public policy rather than bedroom policy," Strober echoed.
An Economic Boon
Whether or not partnership equity explains falling birthrates, Goldin, Strober, and Davisson all champion it—Davisson's book even includes checklists to prompt couples' conversations. And equity remains an economic concern in its own right.
"If you begin with the thought that talent and creativity are distributed among women and men, why would you not want to use both distributions and take the top of each to run your economy and your society?" Strober asks. "In terms of economic well-being, social well-being, use of resources—you want to look equally among men and women."
Davisson, mother of two boys, adds: "I really value that my children see their father in food-preparation mode all the time—he's the family chef. They're going to grow up thinking that's totally normal. The value is both for the workplace and for the citizens in it."