[ben_w]

The population indeed went up, and at the same time the fertility rate is declining. What Malthus was expecting is that more food would just lead to more people on the knife-edge of famine, and we're wildly far from that in most of the world. (What is paradoxical is that the USA is simultaneously very rich, has high obesity, and somehow manages to also have a huge problem with kids going hungry).

The very specific point I'm claiming is that the increased consumption isn't always unbounded.

[hhdhdbdb]

Why is fertility declining? I posit we are hitting non-food constraints. Political ones. Land use constraints. If you build millions of homes fertility will go up.

[HappMacDonald]

In wealthier, modern economies:

* More women work more and invest in their own education and fewer spend time alone at home as they might in poorer countries which would facilitate giving birth and investing time on childcare that way.

* More men and women derive their primary income from work that children cannot easily participate in. EG: office work, work from home computer work, vs farming or working with one's hands. In many poorer countries it is common practice to have more children at least partially to bolster the labor force around the house.

* Wealthier nations have better access to family planning: contraception, abortion, pasttimes that can meaningfully compete against getting laid in the first place.

Sources: Colleran, H., Snopkowski, K. Variation in wealth and educational drivers of fertility decline across 45 countries. Popul Ecol 60, 155–169 (2018). https://doi.org/10.1007/s10144-018-0626-5 https://link.springer.com/article/10.1007/s10144-018-0626-5

More Work, Fewer Babies: What Does Workism Have to Do with Falling Fertility? - Laurie DeRose and Lyman Stone https://ifstudies.org/ifs-admin/resources/reports/ifs-workis...

[ben_w]

There are millions of empty homes in this world.

I'd assume environmental, but there's also more subtle answers than will fit in a comment box — whatever the cause, it has to be near-global.

China's building loads more houses, still has a fertility decline.

[shadowmnifold]

Surely, the reasons are multivariate with all kinds of interactions and feedback mechanisms between the variables.

It is really a good example of what natural dimension reducers we are, even when we know it makes no sense. It is like we can't but help ourselves to reduce things to one explanatory variable.

My favorite is the news headline "The market went up today because of X".

[hhdhdbdb]

They never say that.

They say: Tesla shares up as revealations surface that the wind is blowing east.

[hhdhdbdb]

Yes I forgot to mention the implied: Homes, that meet code, with connected utilities in places people want to live that are not being landbanked.

[AcerbicZero]

The fertility rate trends are missing the core point here. Your obesity and hunger examples actually reinforce the Jevons paradox - when a resource becomes cheap enough, we find ways to use it even beyond what seems rational. But more importantly, you're still not getting the original Malthusian comparison: Malthus wasn't predicting that cheaper food would make people eat more (obesity) - he was predicting that cheaper food would lead to more total people. Similarly, cheaper AI won't just make individual AIs consume more - it means AI will be deployed everywhere possible. The parallel is about multiplication of instances, not increased individual consumption.