Most of the world does not have a shrinking population. The birth rates may be below replacement, but populations are still growing as the age structure shifts. Japan has achieved true negative population growth.
Every country in the developed world plus the former Warsaw pact members have negative natural population growth. They're being propped up by immigrants, that's why they're populations are growing. For example France has about 67 million people but the number of natives is estimated to be around 50 million. Which would be about their population in 1971, 50 years ago. Similar story with the UK, Switzerland, the US, etc. In Japan it's just visible because they have negligible immigration plus even lower birth rates.
I've counted. 235 countries and territories. 30 are downright decreasing.
Plus:
> As of 2010, about 48% (3.3 billion people) of the world population lives in nations with sub-replacement fertility.[2] Nonetheless most of these countries still have growing populations due to immigration, population momentum and increase of the life expectancy
That was back in 2010 and fertility rates are only going down plus Covid has accelerated this so I'm willing to bet real money 50%+ of the world's population is living in countries with net natural population loss due to low fertility rates.
These things are very localized, look at the world map on that page to see where this growth is concentrated.
It isn't all bad. The aging population will have to be supported by fewer people, which is obviously a problem, and one that can really only be solved by asking the elderly to work to a greater age.
On the flip side, Japan has incredibly dense cities with tiny houses. As the population drops to half its current level there will also be more space for living decently, with bigger houses, more green spaces, etc. It's not at all impossible that in such a situation, women may choose to have more children again.
That's at best a temporary situation though. If births are below replacement rate, at some point the population will also drop. People aren't going to age indefinitely.
The blue countries are below replacement rate, and represent most of the world. Green countries are at replacement rate. The rest is above, and are all in Africa except for Afghanistan and Iraq.
