For every year a woman ages, she must earn $7,000 more annually to remain equally attractive to potential romantic partners, according to new research from Wharton professor Corinne Low that calculates the economic trade-off for women between career and family investments.

In two forthcoming papers, Low, a professor of business economics and public policy, takes a revealing look at “reproductive capital,” a term she uses to describe the economic value of fertility, and thus the trade-offs that women make when they make time-consuming educational and career investments.

In her first paper, “Pricing the Biological Clock: The Marriage Market Costs of Aging to Women,” forthcoming at the Journal of Labor Economics, Low designed a unique online dating experiment to determine how both men and women fare in the marriage market as they get older and fertility declines.

“You always hear people talking about the biological clock and how influential it is in women’s lives. But what’s been missing from the literature is this idea that if men also want to have kids, then it isn’t just a personal trade-off for women, it’s an economic trade-off,” she said. “Who you marry is one of the most significant financial decisions you can make. It’s a big deal for your financial well-being whether you marry someone who is going to make $50,000 a year or $500,000 a year.”

The experiment recruited real online daters who were asked to rate hypothetical profiles in which the photo was the same, but the age and income varied. The participants were incentivized to be honest in their answers; as compensation, they received customized advice from a dating coach on how to attract the type of partner they rated highest.

The results found that both male and female participants valued a high income in a potential romantic partner, but there was a sharp contrast when it came to age preferences. Men were rated higher as they aged, while women were rated lower as they aged. However, the preference for younger women was only found among male daters who had no children and who were knowledgeable about when female fertility declines. Based on their ratings, for every year past 30, women had to make $7,000 a year more to stay in the romantic running for them.

“These findings indicate that men also hear the ticking of the biological clock. Seeking to marry and have children, they naturally prefer more fertile partners,” Low wrote in the paper.

More Equitable Policies

Low said she hopes business and political leaders will use her findings to craft more equitable policies that take into consideration this economic trade-off for women. Although women’s education levels have been rising rapidly in the last 50 years, women still make up just 8.8% of Fortune 500 CEOs. Keeping talented women in the workforce isn’t just important in closing the gender pay gap, it’s a key component to a thriving economy, she said.

“Who you marry is one of the most significant financial decisions you can make.”— Corinne Low

“You might be paying her more money to stay in this high-pressure job, but she’s losing out on the marriage market, which puts it in different economic terms,” Low said, noting that women’s fertility begins to decline in the 30s, which is the same age that most careers ascend. “Firms need to think about how to alleviate that trade-off and recognize it as the equivalent of costing her money.”

She said change could come in the form of redesigning career timelines so that women can get the full value of both their human and reproductive capital. In law and medicine, for example, women often delay marriage and children as they attain graduate degrees and pursue residency or partnership.

“There’s no reason you shouldn’t be able to finish law school, take a fellowship that’s a slower pace for a few years, and then start the partner track when your kids are in kindergarten,” Low said. “People are working into their 70s these days. Why can’t they make intensive investments starting when they are 35?”

Human vs. Reproductive Capital

While Low’s first study finds a $7,000 price tag on each year marriage is delayed, her second study, “The Human Capital – ‘Reproductive Capital’ Tradeoff in Marriage Market Matching,” forthcoming at the Journal of Political Economy, models the real tradeoffs this consideration creates in women’s school and career investments.

People who are higher income or higher education typically marry partners who are also higher income or higher education. This is a phenomenon economists refer to as “assortative matching.” Low documents a key deviation from this pattern: Throughout the 20th century, graduate-educated women have married poorer spouses than college-educated women, despite being higher earning themselves. Every other education level yields richer spouses.

Why? Education may increase “human capital,” but because it takes time, it decreases “reproductive capital,” especially for educational investments that take longer and are later in life.

Low shows that when you acknowledge this duality in women’s school investments, you can predict that education will be viewed as a positive thing in the marriage market, up to a point, but will start to detract from women’s marriage market “value” when it interferes with fertile years.

Low said her research illuminates how women pay for investing in their careers and education with a “tax on the marriage market.” This makes entering careers requiring lengthy investments, which also tend to be the highest paying, less appealing for women, and may help explain the persistent gap in representation for women at the top of the corporate ladder.

“You might be paying her more money to stay in this high-pressure job, but she’s losing out on the marriage market.”— Corinne Low

It’s not all bad news, though. Recently, graduate-educated women have started marrying richer men than college-educated women, and also marrying at higher rates and divorcing less.

Low’s explanation: the shrinking American family. Because everyone is having fewer children, graduate women aren’t facing quite the same disadvantage. The preference for smaller families seems to be a bit of an equalizer for women across the board.

“People have documented this phenomenon of a reversal of fortune for educated women on the marriage market — that they used to marry less, get divorced more, have fewer children. And now, things are improving. But I show this has not been driven by college-educated women at all, but rather graduate-educated women, and that’s because of reproductive capital,” Low said. “A graduate degree and the subsequent career investment really do cut into those reproductive years when you want a large family.”

Low’s work further suggests that this marriage market improvement could be leading to a greater willingness for women to pursue educational investments, with women’s graduate school enrollments now outpacing men’s.

Women as ‘Economic Agents’

When asked if she found these studies to be a disappointing indictment about gender in society, Low said it was simply honest.

“There are some real difficulties, and we can build a better society that lets us be more equal by taking account of those differences,” she said. “But we don’t get there by ignoring those differences and gaslighting women that they can just try harder.”

Low, whose research focuses more broadly on diversity, equity, and inclusion, said the two papers are part of her larger agenda to change how women are studied in economics and beyond. She wants society to value women as “economic agents” and treat women’s issues with the same weight as other serious topics. Whether or not to have children — and when to have children — is a fundamental decision.

“If you look around the world, you see not everybody consumes cars or designer clothes, but most people get value in their lives by either having or connecting to children in some way,” she said. “Children are of fundamental economic importance, and I want to treat that with the full seriousness of the economic tools that we have. In doing so, it takes women’s decisions out of this dismissive context and puts it back in the domain of economic optimization, where there are two very important sources of value creation that she’s trading off between.”