There is a certain type of problem whose sheer time scale makes solutions difficult: The longer the time between today’s decisions and tomorrow’s catastrophes, the harder it is to demand sacrifices now in order to ensure those catastrophes never happen. Climate change is the obvious example.

But it’s increasingly clear that there is another: population decline. As the problem of falling birthrates attracts more concern — and previous efforts to reverse it have proved insufficient — a growing body of research indicates that a genuine solution will require a paradigm shift in society’s understanding about what is worth paying for and who ought to pay it.

Across most of the world, fertility rates are falling. As economies develop, fertility rates tend to decline — and when economies develop especially quickly, fertility rates often plummet to particularly low levels. In many countries, they are already below 2.1 births per woman, the “replacement level” needed to keep populations steady from one generation to the next.

If current trends continue, by 2050 more than three-quarters of countries will be below replacement-level fertility. By 2100, populations in some major economies will fall by 20% to 50%. And because birthrates compound like debt, the further fertility rates drop in one generation, the more they would need to increase in the next one to make up the numbers.

If birthrates do not change, the eventual result would be human extinction. That is a long way off, but population shrinkage is likely to have severe consequences far sooner. As the ratio of working-age adults to dependent children and retirees falls, there are fewer workers to support the social safety net. The result is that taxes rise, the quality of public services deteriorates, and the economy eventually shrinks.

Politicians, policymakers and the public increasingly realize that this is a serious problem. And yet despite a variety of financial incentives, ad campaigns and other policies, birthrates have continued to fall.

The work of Nancy Folbre, a feminist economist at the University of Massachusetts, Amherst, suggests that the problem may be that existing programs are simply too small to make a difference to the real issue: that as countries get richer, it becomes much more expensive to be a parent. That’s not just because out-of-pocket costs rise, though they do. Rather, the bigger issue is the cost of the time parenting requires, which, while unpaid, is not free, and in fact becomes vastly more expensive as economies develop.

In 1994, Folbre published an article with a provocative claim. “Individuals who devote relatively little time or energy to child-rearing,” she wrote, “are free-riding on parental labor.”

Free riders, in economics, are people who benefit from goods or services without paying for them. Because all citizens of the United States have claims on children’s future earnings via the money they will pay to support Social Security, payments on public debt and other programs, she argued, people who enjoyed those benefits without doing the work of childbearing and child-rearing were free-riding.

In fact, she pointed out, parents actually take a double hit because unpaid child care work, which represents a huge component of the cost of parenting, is also left out of the benefit calculations for government programs like Social Security. So the parents who give up some or all of their paid work to care for children not only lose income in the short term; they also get a comparatively smaller share of the public benefits in the future. Nor can unpaid work be saved in a tax-advantaged account like a 401(k), putting parents further behind in accruing private retirement savings, too.

Folbre’s argument is not merely that the current system is unjust but also that it makes little economic sense. The failure to compensate people for the unpaid labor of child-rearing creates a disincentive to have children, and therefore leads to falling birthrates that harm society as a whole in the long run.

Government programs like Social Security have, according to this argument, taken many of the financial benefits of children and shared them with the wider public. At the same time, the private costs of childbearing have skyrocketed, because the rising wages available to parents in paid work make the opportunity costs of doing unpaid work rise, too.

When parents cut back on their hours at work to take care of their children, for example, they lose income. And even if they work full time and pay for child care, the child care and related housework they do before and after their paid jobs still carries opportunity costs: foregone overtime, leisure, sleep and investment in other relationships.

One standard prescription for free-rider problems is government intervention, either to shift more of the costs of production onto society or to privatize more of the gains from it. For parents, that might mean boosting Social Security payments for each child they have or giving them tax credits or direct subsidies.

Many governments already offer at least some subsidies to parents to defray the costs of child-rearing. The United States, for example, gives most parents a tax credit of up to $2,000 per child per year.

Some countries, like the Nordic nations, offer parental leave policies and state-subsidized child care that reduce out-of-pocket costs to levels that most American parents can hardly dream of. Still, these paradises of cheap child care, socialized health care and inexpensive universities are in the same declining-population boat as most of the rest of the world.

Although benefits are generous, the prices of food, housing and paid child care are so high in those countries that parents are still left with higher out-of-pocket costs than elsewhere, a 2023 study found. State subsidies offset only a fraction of the high out-of-pocket costs for things like food, housing and paid child care. And high wages increase the value of parents’ unpaid time.

Based on out-of-pocket costs alone, if the average parent in Sweden suddenly became a nonparent, they would be able to consume 55% more in goods and services over their lifetime. In Finland, they would be able to consume 50% more. The average European parent in the researchers’ sample, by contrast, would be able to consume just 31% more.

When the value of parents’ time is added in, the numbers grow even more extreme. The hypothetical nonparent in Sweden would be able to consume 164% more over their lifetime, and the Finnish one 146% more. The average European, by contrast, would consume just 108% more.

There is some evidence that cash transfers to parents do make a difference to fertility rates. The research of Lyman Stone, a senior fellow at the Institute for Family Studies, a conservative pronatalist think tank, suggests that fertility rates rise about a quarter of a percentage point for every percent of GDP that governments spend on cash transfers to parents.

“For the U.S. to buy its way to replacement rates — so to go from our current 1.6 to 2.1 — to do it in the long run would probably cost $700 billion to a trillion dollars a year,” Stone said.

That is an eye-watering amount of money, even if the target was to stabilize populations over time rather than reach replacement rates immediately. But if children are social goods, then in financial terms, it would be an investment.

“It’s inevitably a matter of public values and public commitments.

“You have to decide what you care about and what you’re willing to pay for that,” Folbre said.

“We have to figure out what our priorities are and what we think the value of a human life is.”