Our country faces a very real risk of demographic stagnation in the near future, because both fertility and immigration are in speedy decline.

These trends will have unfortunate consequences. With slower population growth, we’ll see slower economic growth and less economic dynamism — as there just won’t be economic space for new firms to grow.

Many Americans are rightly worried about the trend, but the proposed solutions are often diametrically opposed: On the left, some call for increasing immigration, something the current administration is, let’s say, not keen on. On the right, we’re seeing a growing number of advocates for pro-natalist policies, some of whom deploy racially charged rhetoric. (I’m an advocate for both approaches, sans the racism.)

But there’s a tiny problem. These policy-driven solutions will fail. Even with comparatively open immigration policies, the reality is that the surplus population of our Latin American neighbors is running out. Fertility has fallen sharply in Latin America, as incomes rise, so immigration has been naturally falling and would continue to do so even if immigration policy remained unchanged. Plus, in a departure from past trends, immigrants increasingly have similar fertility rates to US natives (or even lower in the case of many Asian immigrants).

So while immigration can be a useful stopgap, it won’t bail the US out of stagnation in the long run.

The answer, therefore, may involve changing not only policies but also cultural norms — and a good place to start might be something as simple as babysitting your neighbor’s kids.

Before we get to why that’s so, let’s talk a bit more about American cultural norms surrounding childbearing and parenthood — which are, in turn, shaped by the deep structure of our modern economy.

As more years of education become necessary for economic success, childbearing is postponed. Changing sexual norms, too, lead to postponed marriage, the main driver of fertility rates.

Government policy tends not to affect fertility much

Financial incentives — such as the child tax credit, recently expanded in the Republican tax reform (an effort spearheaded by Sens. Marco Rubio (R-FL) and Mike Lee (R-UT)) — have been empirically shown to have very small effects on fertility, while the best academic literature suggests progressive policies like family leave or free child care have even smaller effects.

To actually make a substantial difference, we need to take a look at our own lives, at our collective behavior. The key to a society-wide change in fertility may not be in Washington at all but in the small decisions of individual households.

The case for fertility being culturally driven is strong. When respected cultural figures encourage childbearing, the research shows, childbearing tends to rise (as when the patriarch of the Georgian Orthodox Church promised to personally baptize any children families had beyond two). When respected cultural figures discourage childbearing, childbearing tends to fall (as when MTV aired shows covering teen moms in unflattering fashion). And it’s widely demonstrated that religiosity influences fertility (and probably vice versa).

Of course, our nation’s leaders are unlikely to suddenly start speaking with one voice in favor of having more kids, we can’t order Hollywood to produce positive portrayals of parenting, and 90 percent of Americans aren’t about to convert to a religion that promotes fertility.

But here’s one small thing we can do: We can volunteer to help the parents we already know. Whether you’re a Catholic integralist planning to raise a battalion of little kids, a social activist wanting to build community solidarity, or a militant atheist aiming to undermine the material attraction of church life, you should be able to get on board with babysitting the neighbor kids.

Note that since 1991, average child care costs have risen by 180 percent, as general consumer prices have risen just 80 percent. This phenomenon is known as “Baumol’s cost disease,” after the late economist William Baumol. Basically, because US labor productivity and earnings have been rising sharply in some sectors, like tech, they bid up the price of those sectors where there has been very little innovation — like child care. Industries vulnerable to this disease tend to be dependent on human labor, and they aren’t amenable to scaling up. (The average child care worker today doesn’t monitor twice as many kids as 30 years ago, nor would we want them to.)

Perhaps as a result, the time parents spend directly “parenting” is rising — and not just on the fun, quality-time stuff like reading together. Parents spend more time even on basics. The graph below shows average hours per week spent by parents on “physical care” of their children, per child under the age of 5, from 1965 to 2012.

Could it be that parents are simply less efficient now? Maybe. Smaller family sizes mean parents can afford to spend an extra five minutes getting their kid to eat just one more bite, and that’s not really a bad thing. But surely at least some of this is the result of less help from non-parents.

Observe that the share of non-parents who spend any time watching other people’s kids has been falling over the past 15 years.

In other words, childless people like me are becoming more and more unreliable babysitters, leaving parents out in the cold.

This is an especially unfortunate situation because there are more potential babysitters today than at any time in recorded history. We can track the number of adults with no kids under age 5 compared with the number of adults who do have a small child all the way back to 1850.

There used to be three (or even fewer!) adults with no child under 5 for every adult who did have a child under that age. But today, we have nearly 10 people with no little kids for every person who does. The upshot of that statistic ought to be that parents shouldn’t be feeling isolated or overwhelmed by child care! There’s lots of help nearby.

So why are parents shunted into market-based child care, with its explosive cost growth?

The answer is simple: cultural norms. Retirees may move to be near their grandkids, or they may move to Florida. They’re mostly doing the latter (in fairness, maybe partly so the grandkids will visit them in a nice touristic location). Parents may make an effort to live near extended family, but modern employment arrangements don’t make that easy. Voluntary intergenerational living is increasingly rare.

When facing Baumol’s cost disease, economists generally say there are two solutions: Either find a substitute-product for which productivity is increasing or innovate to create productivity. I don’t know how to make a day care twice as productive, but I do know how to help parents substitute away from market-based child care if they want to: I can volunteer to watch their kids for a Saturday, or overnight on a Tuesday.

If non-parents donated one night a month. that alone could make a substantial difference in parents’ lives

Let’s say that a mere one out of every three people with no child under the age of 5 is a reasonably competent babysitter, meaning they can keep a child alive, fed, and unharmed for 12 hours. You might wonder how often this competent subset would need to babysit to give every parent with small kids one night (or weekend day) off per week.

The answer may surprise you: just once a month. If just a third of those of us with no small children committed to watching someone else’s small children one time in a month, free of charge, we could give every parent a night off weekly.

Surely we all want to live in a society in which House of Cards or poker night is a lower priority than investing in the smallest, most vulnerable members of our society. And isn’t it obvious that we should all want to lend a hand to those citizens who make the societally essential, forward-looking choice to become parents? (After all, who will fund tomorrow’s Social Security?)

You were taken care of by friends and family for free when you were a screaming poop factory; moral reciprocity demands that favor be returned, even if you, like me, really strongly dislike screaming little poop factories.

So this weekend, you have a chance to strike a blow for the future, be a hero to a parent. Find that friend who you lost touch with once they had a kid. Call them. Offer them the chance to pick one of three nights or days when you could take their kids for at least five hours.

You can even offer to grab the Pack ’n’ Play and take their child to your house. But whatever you do, make one thing clear: You care about them, you care about their child, and you want to help.

The future depends on finding some way to keep American population growth up. If we fail, putting it plainly, the future will include insolvency of our social aid for the elderly and the poor, a permanent decline in economic dynamism, huge swaths of the country locked in intergenerational economic depression and an ever-increasing burden on women in particular, as family life becomes less compatible with a career.

A little babysitting seems a small price to pay to avert those consequences.

Lyman Stone, a Vox columnist, is a regional population economics researcher who blogs at In a State of Migration. He is also an agricultural economist at USDA. Find him on Twitter @lymanstoneky.

The Big Idea is Vox’s home for smart discussion of the most important issues and ideas in politics, science, and culture — typically by outside contributors. If you have an idea for a piece, pitch us at thebigidea@vox.com.