Who says economic determinism is dead? The yet-to-be-fully-broken-down decennial census released yesterday makes clear that the link between economics and reproduction isn’t only one of correlation but also, more decisively, of causation.

The decade just completed saw the second lowest rate of American population growth of any previous decade (7.4 percent) save that of the 1930s (7.3 percent). What those two decades have in common, of course, were the long depressions triggered by a financial meltdown in the last years of the preceding decades. In the ’30s, confronted by a massive disappearance of jobs, young people took to the road and the rails (boxcars more particularly) in search of sustenance, and those who stayed put were seldom in a position to start a family.

Were the years 2011 through 2020 really a decade of depression? For young adults, they came very close. Youth employment was slower to recover than general employment, and there were a host of other factors that put childrearing and family formation out of reach. First, the service sector jobs open to the young were disproportionately low-wage. Second, even for young people with decent jobs, student debt payments significantly reduced the capacity to support children. Third, the kind of income that was increasing during the 2010s was income from investments, not work, and investments require the kind of income that young people didn’t have. That’s why the median age of parents at the birth of their first child continued to rise.

Conversely, the decade in the past 100 years to have had the greatest rate of population increase (18.5 percent) was the 1950s. That wasn’t due to immigration, which had slowed to a trickle as a result of the law restricting immigration from anywhere but northwest Europe. It was due, rather, to the broadly shared prosperity of the postwar era, when the rate of income increases was actually higher among the middle class and the poor than they were among the wealthy. At the time, the nominal tax rate on truly rich Americans was roughly 90 percent—an all-time high. Also at the time, the rate of unionization was roughly 35 percent—also an all-time high. The share of workers who made a "family wage," enabling them to support a spouse and children was also, not coincidentally but causally, at an all-time high, too. As the share of workers making that family wage began declining (in tandem with the rate of unionization) in the 1970s, the share of families in which both parents worked rose correspondingly.

And so, to today, when levels of income in households with two working parents often don’t keep pace with the rise in rents and health care costs, and when you factor in the cost of child care, too—voila: just 7.4 percent population growth. The other contributing factor to slowing growth, of course, was the decline in immigration—and there, the absence of jobs in the first part of the decade loomed larger even than Trump’s wall and nativism in the second half.

How, then will those Trumpians react to these numbers? (If they react at all, as the subject of President Biden’s nonexistent war on hamburgers seems to about all their vexed little crania can handle just now.) To the disproportionately elderly cohort within Republican ranks, the declining share of young, working Americans poses a threat to such support systems as Medicare and Social Security. Indeed, in developed economies with low rates of childbirth—most of Europe and Japan—the financing to support their increasingly elderly populations is plainly endangered. And here in the U.S., absent a more welcoming immigration policy, a governmental intervention to wipe out student debt and fund child care and universal pre-school, a substitution of permanent status for the one-year child tax credits in President Biden’s American Rescue Plan, and the kind of union growth that would follow the enactment of the PRO Act—in short, absent the adoption of a range of progressive policies—there’s no reason to think that our rate of childbirths and population growth won’t continue to decline.

Bigots like Tucker Carlson fear "replacement" by a more racially diverse nation. If their opposition to the kinds of reforms I’ve listed above blocks progressive change, however, the pool of "replacements" of any kind will continue to dwindle.