America’s alleged “baby bust” is pushing the country over “a demographic cliff.” So argues Jonathan V. Last in The Wall Street Journal. Stacking one highly debatable claim on the next, Last builds a palace of hooey, in the basement of which sits a conservative agenda that’s not very conservative.

Here are the agreed-on facts: America’s fertility rate — the number of children born by the average woman — has dipped below the replacement level of 2.1 children per woman. Were it not for immigrants’ having more children, it would be lower still. All arrows point to it going down further, as the Latino fertility rate plummets. (In Mexico, it’s at the replacement level.)

All this is true, but where is the problem? The problem, says Last, a writer for the conservative Weekly Standard, is that “growing populations lead to increased innovation and conservation.” Sure, more people mean more Albert Einsteins, but they also mean more Jeffrey Dahmers.

My questions are these: Is today’s America cleverer than 1954’s America, when the population was 150 million smaller? Teflon, McDonald’s and, er, the birth-control pill were all invented that year. By the way, how are Niger, Guinea-Bissau and Afghanistan, with the world’s highest fertility rates, doing in the innovation department?

Last’s effort to link a growing population with “conservation” is heroic but a crock. “America’s environment has become much cleaner and more sustainable,” he says, “even though our population has increased by more than 50 percent.”

Actually, these improvements happened despite enormous increases in population. And the environment has gotten better only by some measures. Our growing human population continues to run over natural habitats, pushing many species into extinction. There’s also a bit of elder bashing. Last impolitely refers to aging boomers as “the bloated cohort of old people.” Falling fertility can result, at least in the near term, in a society more weighted with the elderly, he notes. The result is “capital shifts to preserving and extending life.”

What’s wrong with that? Developing drugs for Alzheimer’s is also innovation. Why is spending our capital on health care less admirable than devoting it to smarter cellphones or new cable programs?

Meanwhile, a decline in the working population encourages the invention of labor-saving devices. Facing a sharp fall in population, Japan has become a leader in robot technologies.

I do not kid: Last worries that the Social Security safety net acts as a disincentive to have children. Traditionally, care of older people fell to grown-up children, he explains. Certainly, that’s how it was done back on the farm in 1890.

Last speaks of vague proposals “to dismantle this roadblock.” One would greatly hike the child tax credit. Another would exempt parents raising children from payroll taxes. The latter could be a slick way to defund Social Security, and thereby kill it.

Other prescriptions include a “welcoming attitude toward immigration and robust religious faith.” The United States takes in more legal immigrants than the rest of the world combined. We’re already welcoming.

And if by “robust religious faith” Last means strengthening respect for traditional marriage and the children born within it, that would be a positive thing. But for all the joys, raising children costs money, both in outright expense and a parent’s lost potential income. In service to that higher mission, conservatives might consider dropping their habit of equating wealth with “success.”

Ahhh, social engineering for conservatives. Putting the word “smart” before “pronatalist policies” does not make them something else.

My favorite proposal is improving highways to help families leave congested cities for lower-cost areas. Gosh, if there were fewer people, there would be less congestion, and no one would have to move.

Froma Harrop is a Providence Journal columnist. Her email address is fharrop@projo.com