Or, why I’m short-sighted enough not to panic about “depopulation.”
A while ago the New York Times ran this unfortunate essay by the economist Dean Spears. Oddly, someone from the Times emailed me before they published it doing “due diligence” on the authors (there was apparently originally a co-author). I said they looked like mainstream scholars with legit credentials, but I didn’t assess their work in detail. But, I added, the term ” ‘depopulation’ is, from my perspective, inflammatory and unhelpful.” Sadly, that advice was ignored, and the Times piece ended up describing earth as “a depopulating world,” and pointing out, “Nobody yet knows what to do about global depopulation” — without ever defining the difference between “depopulation” and regular old population decline. I think the point was made by the dramatic graphics, though, from Times artist Sara Chodosh. This one in particular:
OK, point taken. If the world’s fertility rate falls to the 2021 US rate of 1.66, global population will decline. But how much and how fast? This graph has no axes! And even if it did, a time scale of 5,000 years is too hard to grok. I call axis manipulation. It is not a helpful guide to whether or not it’s time to panic about depopulation — even if its projections were reasonable (which, again, I haven’t really evaluated).
Fortunately, the essay links to a preprint by Spears and colleagues, and that links to a repository that seems to have the data for the projections he used in the essay. I’m not completely sure, but I think my figure below uses the data from the thick red line above, the USA-level fertility scenario. If you add some axes, and cut the x-axis down to just 700 years, it looks a lot less scary to me. By this scenario (in which the global total fertility rate falls rapidly to 1.66), by 2205 — 181 years from now — we would be back down the the global population level of the year 2000. I added labels for those points:
Now, if you go out another thousand years in this scenario, the population does fall to zero (round numbers) in the year 3255, which would be concerning. Or:
I am just too short-sighted to panic about this. A lot is going to change in the next two centuries, no doubt about it. I just am skeptical that population decline — from falling birth rates, at least — is going to be the number one issue. And, if our descendants manage to solve the other existential crises we are leaving them, then (a) I think they might even be glad to have a little less upward population pressure, and (b) people might decide to start having (or printing or whatever) more children, too.
Family Inequality 
I kinda wonder if Musk’s concern about population decline is disingenuous. It may be more like a justification for him to have 9 kids, but deep down he feels bad because he doesn’t spend much time with his 9 KIDS. Or he feels the need to justify his messy personal life, similar to how he likes to blame schools or society for his estranged relationship with his oldest son. Like seriously, even some who had 10 million dollars a year in income without running a business would have a problem spending time with 9 kids from three different women, let alone if he ran two businesses and a Twitter addiction. Have any of these “natalist” rightists or leftists (Mathew Yglesias) criticized Elon Musk for spending time on Twitter rather than his 9 kids?!? And can we all admit that if there was a rich African American NBA player, but had 9 KIDS and spent a ton of time on Twitter, the right and even some moderate leftists (maybe Mathew Yglesias) would attack him for it, or do some chin-stroking saying, “Well, he should be a better Dad and spend more time with his kids.” Maybe Lyman Stone or Bradfor Wilcox can get some money from a right-wing think tank to attack Elon Musk for being an absentee Pops? Or is that the job of “elites” to attack Musk but of course not the non-elites that populate right-wing think tanks.
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I think underpopulation is likely to be one of the major concerns of the latter part of this century…I wouldn’t venture to comment on anything beyond that, there is just too much that could happen in between 🙂 But as I understand it, America is doing pretty well at 1.66. China is at 1.2. And the problem isn’t really “depopulation,” is it, it’s what happens economically when you have a country with many more old people than young people. This could turn into a spiral where young people have worse prospects, and even fewer children, couldn’t it?
Just as a note, it seems to me that world culture is moving in the direction of caring more and more for children, devoting ever more time to them. This is (often) great for kids, but not at all good for the fertility rates.
In general, the world is industrializing (and post-industrializing), and less agricultural countries have fewer children, take better care of them, and have fewer children still. The question is: as we move down this curve, what will happen next? I have no clue, and I don’t think the UN does either 😉
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