Great article! I think that a big problem about the future demographics is the % of the world population that will be elderly could increase substantially. This will deplete retirement plans and healthcare plans if there are not enough young people to replace retirees in the workforce.

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This is a good article. For your growth curves, some people don't see to understand the difference between velocity and acceleration. I also appreciate that you try to be an empiricist. As for quoting articles from Scientific American, indeed, it isn't the 80s any longer (when Scientific American was good). Today SA is replete with political nonsense, so seeing a dumb article such as the one you describe, is today, par for the course.

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Loved this! But what are the reasons why wealthy millennials and Gen Z opting out of parenthood? Most of my gen z friends are saying they're afraid of climate change, they think we are overpopulated & there are not much opportunities for kids in the future. Also Anti-natalism is on the rise in gen Z. They think having children is a burden. What role does the new cultural movements play when it comes to Anti-Natalism?

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Brilliant analysis, Dan. Embarrasses me, as I would have made the same mistake that Oreskes--who is a colleague of mine--made!

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Mar 8, 2023·edited Mar 24, 2023

All of this is fine and relevant, and I agree with much of what’s been noted, both in the comments and in the essay. Humanity was at about three billion people when I was a nerdy pre-adolescent, and I’ve been making population projections in my head ever since.

But there’s a new elephant in the room. I know some people will scoff or sneer, but the expansion of humanity beyond Earth seems likely this century unless there is a dramatic collapse of global tech civilization beforehand. While such a collapse seems distinctly possible, that possibility itself is one reason an increasing number of people are talking about establishing self-sufficient habitats beyond Earth. I’m one of them. I even created a bumper sticker in the late 1970s: “Conserve Earth - Colonize Space” … and a button: “Decentralize - Get Off The Planet.”

(I don’t have any problems with the word “colonize” because I’ve always used it in the biological sense, and the term is often used in ecological studies.)

I’m not a fan of Mars colonization, though, which is what Elon Musk and some other people are working toward. Why leave Earth and go down another gravity well — even it it’s only one-third as strong — when it will be possible to create many different habitats in orbital space, and with any level of spin-gravity desired? (Zero gravity would likely be useful for some industrial processes.)

And no, I’m not suggesting that there will be mass emigration from Earth to space. But space habitats seem likely to offer opportunities for those who want to have children without contributing to an ecological burden on Earth. Determining how this might affect terrestrial demographics is beyond my pay grade and, anyway, I’m retired. But it would seem that space colonization, if it comes to pass, would have a significant impact on fertility projections.

The resources available from asteroids and comets (and likely the Moon with its one-sixth Earth gravity) are calculated by some to be sufficient to create many large-scale habitats able to sustain a human population in the trillions. (Whether that is desirable is for future generations to decide.)

Of course there are many factors that will determine what happens in the future, and any one of them could have a dramatic impact on any trends and demographic predictions. Advancements in artificial intelligence could make robot care-givers the preferred option, and advancements in biotech could reshape what being a human means. (Keep in mind that the brain is part of the body.)

For the present, I take some solace from the fact that I never contributed any babies to Earth’s population, though I know that my life in the United States means that I contributed quite a lot to resource use and pollution, even with my modest lifestyle. I’m also fortunate to have married late in life to a woman whose son and daughter (from a prior marriage) have five young children among them, and I can participate in their development.

Anyway, I think humanity’s plausible expansion into space is too often still ignored in these discussions.

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Excellent article. I've been arguing the same points for years and decades. 1987 is not 2023. However, I would say people are still talking as if it were the late 1960s, when population growth peaked.

I'm not sure that Cornucopianism "came to prominence in the 1980s" since I rarely saw it get any attention and I would have noticed since I've read Julian Simon and the other abundance authors since the early 80s.

You are also correct that Africa is the big wild card and could swing the global by a billion either way depending on the path taken. The UN has the highest projections for population. I think the models used by The Wittgenstein Center and even more by the Institute for Health Metrics and Evaluation (IHME) are likely to be more accurate and given somewhat lower figures. IHME has global population peaking at 9.733 billion in 2064, declining to 8.758 billion by 2100. two thirds of the difference is due to faster reductions in sub-Saharan African fertility and two thirds due to the lower level of fertility expected in populations with below-replacement fertility levels, particularly China and India. Of course, all models including IHME's have different pathways, so the central path is not the only one nor 100% certain.

One fascinating chart from Our World in Data that you didn't include is "How long did it take for fertility to fall from more than 6 children per woman to fewer than 3 children per woman?" It's amazing. For the UK, the answer is 95 years. For Brazil, 26 years. For Bangladesh, 20 years. For China, 11 years. How many people are aware of this?

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Unaware of anybody still projecting vast growth.

What we don't seem to have a plan for, is the coming end to growth. Our whole economy runs on it, assumes it. Parts of the economy are so happy about the housing shortage. Jen Gerson, a Canadian journalist, did a much-linked column about how nobody will fix housing, because so many people (the ones with money and power already) are doing so well from it.


Our society runs on income-inequality, and the way it's been engineered since the feudal regimes declined, is that the already-wealthy generally capture nearly all the income that comes from growth, be it housing or social media stocks. Those who *invest* in the growth get nearly all the profits, those who *work* to make growth possible, get scale wages.

So the wealthy are not going to like the End of Growth, I would predict.

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Nice. I love data-dense articles like this that look at the reality of the world as it is, rather than the fantasy cartoon version of the world we so often see from pundits and prognosticators.

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