It’s not fewer people that’s the problem, but fewer people too fast. A society needs labor to provide the goods and services people need. If the share of people who do labor (working age) to people who don’t (children and the elderly) becomes too lopsided, the burden on those who work becomes unsustainable. (The Boomers had the opposite: they had a smaller older generation and didn’t have many children, so during their prime years the working age population was much larger than dependants on both ends of the age pyramid. That’s part of the reason why they were so prosperous.)
Going by total fertility rate (children per woman):
2.1 is enough for replacement. No problems.
1.8 means every generation is 10 % smaller than the previous. We can deal with that.
1.5 means every generation is 25 % smaller than the previous. This starts to cause problems.
1.0 means generation size halves every generation. This is not sustainable.
If the share of people who do labor (working age) to people who don’t (children and the elderly) becomes too lopsided, the burden on those who work becomes unsustainable.
Except that raising children requires more time and resources than caring for elderly. So having less children frees up more resources to care for the elderly. Into the next generation there are now less people which require even less resources which means you need fewer workers to produce those resources.
History provides evidence for this. After every major war there were economic booms. This is despite wars killing off the able bodied workers leaving only the sick and elderly.
The only people who suffer from a lower population are the ownership class. They live by skimming a little of the productivity off of every worker.
Except that raising children requires more time and resources than caring for elderly.
Source on this? Doesn't sound right at all. According to my findings after a quick search, LTC (long-term care) takes a significantly higher fraction of OECD countries GDP than e.g. childcare+early education.
Need citation for this. War is a net negative every time. War destroys resources and kills people. This leads to a labor shortage. It also destroys property so it leads to housing crisis and famine.
Except that raising children requires more time and resources than caring for elderly. So having less children frees up more resources to care for the elderly. Into the next generation there are now less people which require even less resources which means you need fewer workers to produce those resources.
That is a death spiral. You can consider the labor involved with caring for the elderly a sort of tax on labor. It's a net drain but required and is directly related to previous generations of labor. The labor involved with raising children is similar but is closer to an investment. The more labor done for raising children, the more labor there will be next generation. Even though the labor for children is higher than the labor for the elderly, it results in a net positive.
If you have vastly fewer children in the following generation, you end up with a higher percentage of elderly labor compared to the labor pool. If the labor for children goes down enough to more than make up for it, you don't have a per capita labor deficit. BUT you do have less total labor.
Now we get into the real issue: maintaining society. It isn't just about the labor to care for each other. But technology, infrastructure, food, etc all need a certain amount of labor. And most of these tasks are scalable so it requires less labor per capita as population increases. If you shrink your labor pool too quickly, you won't be able to sustain your infrastructure causing a collapse.
Napoleonic Wars, WW1, WW2. Not even including the US, Russia, China and Japan all had explosive growth after WW2.
War is a net negative every time.
If a sudden drop in working age labor causes a death spiral, then Russia would have had a death spiral after WW2. Instead they had a boom and put a man in space before the US.
The labor involved with raising children is similar but is closer to an investment.
It's not an investment because at the end of a child's growth, you now have a consumer who requires more resources. When an elderly dies, that frees up resources for everyone.
The Black Plague is a accepted factor for the Renaissance. Labor became more valuable. The death of so many workers allowed the surviving workers wages to increase and they got more independence. It wasn't a death spiral.
BUT you do have less total labor.
Total less labor isn't a problem when you don't need more labor.
If you shrink your labor pool too quickly, you won’t be able to sustain your infrastructure causing a collapse.
WW2 was a far quicker and far more severe labor pool shrinkage for many countries in the world. There was no collapse.
It is a pyramid scheme. We have an economic system based on continuous growth. When it doesn't grow, it's a huge panic, such as during the pandemic or 2008 economic crisis. Now the number of workers and consumers, the base of the whole system, is starting to shrink and nothing much van be done without changing the essence of the system.
Of course those that became rich and powerful because of the system don't want to change the system that keeps them rich and powerful. But without change the system might not survive.
If you're nodding at the concept of overpopulation that's not really a "problem" as we're expected to top out around 15 billion as the rest of the world develops and then replacement rate is expected around 12 bil as things level back out from an earlier peak iirc.