Demographics lends itself to two of Americans’ favorite pastimes — watching trends and arguing about politics.

For decades, experts and everyday folks have debated the perils and promise of expanding or contracting the national population. But no clear consensus emerged, especially when it came to birth rates. Divides over national culture and national policy ensured that. Now, however, the latest numbers suggest that declining birth rates — here and abroad — are tangled up with exactly the divisive politics we’re so apt to blame for the disagreements that keep us trapped in a dysfunctional moment.

That’s not to say there haven’t been some advances. The 1970s-era fears of a “population bomb” have wisely melted away, replaced instead with concerns that Western-style welfare states and entitlement programs just can’t keep up with societies “graying” rapidly as replacement rates dramatically slow. And the stunning shift among much of the industrialized world, not just the U.S. or the West, underscores how inescapable the new demographic crisis has become. For over a hundred years, the federal government has kept tabs on how many times American women between the age of 15 and 44 give birth. That number, the so-called general fertility rate, counts births per 1,000 women within that range; through the first quarter of this year, that rate sank to its lowest level ever: 59.8.

While Americans confront their lowest birth rate on record, Europe, Japan, and Korea continue to face an even more dispiriting future. Last year, the European Union hit its own grim milestone: while 5.2 million died, just 5.1 million were born — a negative natural population change for the first time in EU history. Japan and South Korea, meanwhile, are expected to lead the world in proportion of senior citizens by 2050. Japan already has the oldest population in the world. South Korea is one of the most rapidly aging.

And even in countries like India, China or Mexico, increased prosperity has come with a harsh trade-off. In an exhaustive new international poll, The Economist concludes that “people in wealthy countries consistently want bigger families than they get. Couples start having children late and find it increasingly difficult. A 30-year-old woman has a roughly 20 percent chance of getting pregnant each month, falling to about 5 percent by the age of 40.” Surveys show that people who overshoot their “ideal” family size tend to be cheerful, not regretful, while people who undershoot are the opposite — especially those who have wound up with no children at all.

The problem here goes beyond the way low birth rates force big changes in lifestyle and raise tough challenges for policymakers. Rather than just inward-facing experiences like disappointment or depression, as a group, low-birth people can share outward-facing experiences with big political consequences. Although individuals obviously differ, it’s striking how far-right politics has been fueled worldwide by declining birth rates — and how far-left politics, mobilizing singletons as an identity group with a specific agenda, has too. (Notably, high-birth-rate groups might even be particularly apt to reject the new political extremes of the low-birth moment, if the widespread Mormon opposition to Donald Trump’s campaign is any indication.)

One of liberalism’s most powerful narratives has long been that progress and prosperity will make politics progressively kinder and gentler; as individuals become more equal and tastes and habits converge, interests and passions will grow gentler and more harmonious, with beneficial results for all. The link between falling birth rates and more extremist politics throws that article of faith in doubt. Fewer and smaller families may well produce more rancor and division, not less. Those wondering about the future of “family values” would do well to begin with this sobering possibility.