Our punditry class, which is increasingly composed of cut-rate political scientists, enjoys gabbling about the urban-rural divide, the eternal electoral battle between red-blooded roturiers and blue-blooded burghers. This residential split is often used to explain the buzzword “polarization,” which is a fancy electromagnetic term for difference of opinion and lifestyle.

Conservatives may outlast liberals after all, if only through the age-old wonder of procreation .

A new analysis in the Atlantic uncovers another way in which urbanites and provincials distinguish themselves other than property size: fecundity. In “The Future of the City Is Childless,” Derek Thompson pens a threnody for the once flourishing megalopolis. New York City actually shrank last year -- a Big Apple first in four decades not counting recession years. The number of New Yorkers leaving the city more than doubled during the same period.

Thompson writes, “There are many reasons New York might be shrinking, but most of them come down to the same unavoidable fact: Raising a family in the city is just too hard.” And by hard, he means expensive. Rising housing costs, combined with the unmentioned price of quality education and social outings, pull city living out of the grasp of middle-income families.

What’s driving up the price of everything urban happens to be what economists praise as a salubrious sign of growth: the continual influx of young, childless adults into dynamic industry. The citified industry most attractive to young workers? Tech and internet, which are, ironically, supposed to be levelling fields unattached to specific geography. It just happens that five counties are home to half of the country’s internet-based jobs. Not only that, but, as Thompson points out, “the richest 25 metro areas now account for more than half of the U.S. economy.”

The cursus honorum of urbane careerism doesn’t include room for family formulation. Cities are so rich and expensive that they’ve priced out the cost of having a child, or heaven forbid, more than one. They are, in Thompson’s words, becoming an “Epcot theme park for childless affluence, where the rich can act like kids without having to actually see any.” I’d leave out the Epcot part; Mickey Mouse isn’t much of a presence where ten-year-olds dare venture.

Thompson speaks mainly to the material difficulties of raising a family in densely populated cities where the price of a two-bedroom apartment rivals a five-bedroom, three-bathroom mansion in San Antonio, Texas. But he misses out on the cultural reasons why aging millennials aren’t interested in making a go at having progeny in the concrete playground. After all, space is a luxury, not a necessity, and, until recently, it wasn’t uncommon to hear anecdotes of parents leaving newborns to sleep in bureau drawers.

Natalism is a culturally outré value to millennials because it rubs harshly against the average twentysomething’s ideal of true freedom as the deracinated individual. Kids tie you down. City living, with its apartment swapping, lack of privacy, ephemeral acquaintances, and emphasis on efficiency, encourages looseness, never getting too rooted.

In his epistolary memoir My Father Left Me Ireland, Michael Brendan Dougherty captures the parental ethic that was so persuasive in his upbringing -- as a member of the so-called Generation X -- and with millennials. “The adult world that I encountered was plainly terrified of having authority over children and tried to exercise as little of it as practicable,” he recounts. “They seemed grateful when a child wasn’t difficult.”

But children are difficult. They’re little bodies and minds, fragile and impressionable, you’re lawfully obliged to shepherd to self-sufficiency. There’s no how-to way to properly parent, no shortcuts or easy tricks. Living in a bustling city where everything is priced at a premium and vanity is a guiding principle only makes it harder.

Thompson says the “childless city may be inescapable” at this point as urban amenities continue to be geared toward those not pushing a pram or lugging around a diaper bag. But, as the divide between married suburban parents and metropolitan dinks becomes starker, should we really worry if our biggest cities lack children? For the more fertile conservative, is it really a concern that liberal city-dwellers aren’t reproducing?

Yes, if only for the U.S.’s long-term viability. The country’s fertility rate is at an all-time low. Societies that don’t reproduce die. More importantly, societies that don’t encourage childbirth are planting the seed, so to speak, for their future obsolescence.

That’s just what our cities our doing, as they build more coffee bars and scooter lanes instead of daycares and sidewalks wide enough for strollers. “Die single, and thine image dies with thee,” Shakespeare warned the childless. The American city is losing its ability to perpetuate itself. What political power heartland conservatives gain from infecund liberals comes at the expense of the nation’s health.