TFR (total fertility rate) plummets because it used to be necessary that it was way higher when the child mortality rate was higher - and indeed a decreased in fertility rate follows a decrease in child mortality with a few years of delay.

Having a child used to be a random experiment and you needed to make sure that one makes it through to care for you when you will be old or sick. Pensions, health and welfare systems and much better child mortality rates make it unnecessary to have many children. A replacement fertility rate of slightly over 2.0-2.1 is/would be fine in developed countries.

> A replacement fertility rate of slightly over 2.0-2.1 is/would be fine in developed countries.

Yeah, but that's now what we're having. My country sits at 1.4, and the only subpopulations with above replacement rate TFR are non-indigenous, so to speak.

South Korea has a TFR of below 1.

Japan has a TFR of ~1.4.

Most European countries are somewhere between 1.4 and ~1.7.

The US is below 2.

The West is dying out, and has been for a while.

But, in South Korea, the replacement fertility rate is already lower than 1, and it keeps decreasing every year.

By the way: if someone wants to look up (total) fertility rates, Our World In Data has you covered, of course:

https://ourworldindata.org/grapher/children-per-woman-un?tab...

(You can change the countries displayed by clicking the (+) sign on the right hand side of the graph. I preselected UK, US, Germany, Iran and South Korea here.)

> A replacement fertility rate of slightly over 2.0-2.1 is/would be fine in developed countries.

And many developed countries are far below that. That's what I read the parent to write about, not the shift from pre-industrial to industrial times.

This is when evolution kicks in. Those that can pair up and have children are more likely to be selected for in future generations

Medicine has improved such that it is far less of an evolutionary pressure. I imagine psychological well being, and wealth are more of an issue. It would be interesting to look at the correlation between mental health and wealth, or if there’s a key point between them.

Or there could be a selection pressure for more social groups of humans, a eusocial society, I can’t remember who suggested that.

Exactly this, but it's also why, whilst we should all be conscious of what we're doing to the planet, I'm not so despondent about our future and population endlessly spiraling out of control. It's been shown that once a country achieves a GDP of somewhere around $6-7k they begin to take a bigger interest in issues like climate change, more efficient energy sources and population control more seriously (China is about there now; India, Indonesia, Thailand and other large population Asian countries are getting there pretty quickly). As a planet with finite resources in terms of food and energy we can support a global population of about 10-11 billion. If it's becoming such that once societies advance to a level of development we see in places like S Korea and Japan that population begins to balance out or even slightly decrease, is that such a bad thing?

The issue here isn't a slight decrease in population. Japan is facing a projected decline of 1/4 of their population by 2050. A change of that magnitude will mean severe consequences for their economy and overall culture. Even China has abandoned their one child policy and now has a birth rate of 1.6. We're sailing into uncharted territory where our only comparable previous experiences are famines or plagues.

The problem isn't just that the total population is declining. It is that the dependent population relative to working population is increasing. This leads to all sorts of distortions to how things are supposed to be.

And TFR means...

Not obvious to me, but it means Total Fertility Rate. From wikipedia, TFR of a population is basically the average number of children that would be born to a woman over her lifetime.

Total fertility rate

One single Google search would have revealed that TFR means Total Fertility Rate.

Actual problem is that writing "TFR" or "Total Fertility Rate" takes a constant time (independent from the number of readers) while everyone looking it up is function of the number of readers.

Your parent comment is right in pointing out that it is not a familiar abbreviation.

I suspect people use obscure acronyms like this as a signal that they're familiar with the problem domain and that you should listen to them.

I did this of course, lets say:

Transferrin receptor, Temporary Fly restriction, Terrain Following Radar, Time Frequency Representation

And a Truck in Thailand is named TFR also...

Becoming inhospitable to humans because of overpopulation in certain areas and skewed economic, political and ecological practices in all areas. This won't be fixed by forcing people to reproduce more. Each region's problems must be tackled differently. For example in India's case it would be madness to encourage even more fertility. This may not be the case in other areas. As a whole the planet has quite enough humans at 7 billion. We don't need so many unless we're planning on settling other worlds which is still more than a century away.

> This won't be fixed by forcing people to reproduce more.

I don't think that was the idea, rather: fix the circumstances and the people will do the rest themselves.

> For example in India's case it would be madness to encourage even more fertility.

And fertility rates there haven't dropped as they did in the developed world, so it's really not the same issue.

It's well established that people (nations and groups within nations) have fewer children as their circumstances improve. Fixing circumstances will lead to fewer children, not more.

This has only been true generally in the West since ~1800 or so. Charles Darwin had fewer grandchildren than children. It’s also not universally true even in the West. Sub populations with higher fertility for the wealthy exist, Mormons and Hasidim for two. Culture beats biology, see Hutterites and the Amish in the US.

> Better circumstances are responsible for low fertility rates, not bad circumstances.

That depends on the definition of "better". In purely material terms, the developed world is the best there ever was. Yet depression, drug abuse, loneliness etc are rising, so maybe humans require more than just material things.

For animals, living in a zoo is the best thing to do. Steady meals, a doctor on call and they'll even bring you mates to reproduce. Yet somehow, many animals in captivity don't want to breed, maybe it's similar for humans.

True, this is a very disturbing development.

Maybe, but IMHO in the grand scheme of things priority should be to stop population growth and thus nothing should be done to encourage births.

I think it's a good thing to both manage population as well as improve well being for individuals.

Indeed. In fact the aim of controlling population is also to improve well being.

But realistically currently controlling population is the aspect that is most important so improving well being should be done in a way that does not result in a higher birth rate.

No, civilization is not becoming inhospitable to humans, this is literally the best time in history to be alive, civilization has never been more hospitable than it is today.

We really do not need more humans, we are not an endangered species. The only reason we think we do is because many societies have essentially created Ponzi schemes where the welfare of the elderly generation relies on ever increasing numbers of younger generations, which will inevitably become unsustainable.

>No, civilization is not becoming inhospitable to humans, this is literally the best time in history to be alive, civilization has never been more hospitable than it is today.

According to the dictionary "inhospitable" means "Unfavorable to life or growth", and it's much harder for me to have one children than it was for my grandparents to have five.