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Comment by nordsieck | Hacker News Reader

> It is a distinct possibility — highlighted in the recent book, Empty Planet — that global population will decline rather than stabilize in the long run. What happens to economic growth when population growth turns negative?

IMO, this is a pretty silly idea.

The fundamental problem with this theory is that there are sub-populations that have been able to maintain high fertility despite the decline in broader society.

For example, the number of Amish doubles every 20 years. Today, there are 1/3 of a million Amish. At the current rate, it'll only be 200 years until there are more than 300 million Amish in the US.

No idea if that will actually happen, but if everyone else dies off, there no reason they wouldn't just take over.

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> The fundamental problem with this theory is that there are sub-populations that have been able to maintain high fertility despite the decline in broader society.

Amish fertility has fallen just as much as overall American fertility has.

"In the modern period, we can see that, from the early 1980s to 2000, Amish fertility had actually fallen way more than U.S. TFR [Total Fertility Rate] on the whole. Then it spiked in the late 2000s, and has fallen since."

This.

There's a reason why religions exist. If they didn't increase the fitness of their adherents, they'd die out rather quickly. We may get caught off guard by shifting demographics and a decline in secular value systems. There are many religions which preach the 'fertility gospel' in one form or another. If the religion is effective in keeping the new generations devout, and that is an important question, we're going to have a population explosion.

> If they didn't increase the fitness of their adherents, they'd die out rather quickly.

Counterpoint:

The Shakers, a Christian sect that enforced complete celibacy (pretty much the definition of decreased fitness) was founded in 1747 and apparently continues to this day [1] (although from the looks of it, it probably won't last another 50 years).

That being said, I largely agree with your point. Religions that make up substantial portions of society are probably beneficial for the fitness of their members.

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1. https://en.wikipedia.org/wiki/Shakers#20th_century_to_the_pr...

Many eastern european countries are very religuous but at the bottom of fertility stats. Some Devout muslim countries are very fertile, others not so. Is congo or angola particularly religious?

> The fundamental problem with this theory is that there are sub-populations that have been able to maintain high fertility despite the decline in broader society.

See https://en.wikipedia.org/wiki/Fertility_factor_(demography)

How do u suppose startups will cater to these 300 million Amish users?

> How do u suppose startups will cater to these 300 million Amish users?

I know very little about the Amish, except that they eschew certain kinds of technology (sort of - Amish tend to be fragmented over this issue) and somewhat insular.

I can confidently say: no one knows what 200 years will do to Amish culture.

It also implicitly assumes that economic growth is the only way for a society to grow.

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