The issue is uneven distribution. While the world fertility rate is trending toward a moderate population decline starting mid century, this will be mostly driv

The issue is uneven distribution. While the world fertility rate is trending toward a moderate population decline starting mid century, this will be mostly driven by extreme declines in specific areas rather than a gradual decline everywhere. There are many developed countries are projected to lose more than half of their populations by 2100 using current estimates. That alone is a major problem for policymakers but what's worse, those estimates have been consistently underestimating the severity of the decline in number of births. In predicting future demographics, there have been longstanding assumptions that the birth rates of countries that fall significantly below replacement will eventually recover. This does not appear to be true, at least on timescales which would appear during any of our lifetimes. Instead, fewer kids reduces social pressure to have kids and results in fewer community resources available to parents (schools, playgrounds, etc). This further reduces the fertility rate. You can see this in countries like South Korea[1] which are seeing rapidly shrinking elementary school populations and have been closing lots of schools as a result. South Korea, always the overachiever, is down to a total fertility rate of 0.82 this year with that expected to fall below 0.8 next year. To put that into perspective, in a country without significant immigration, if that rate were sustained you would come to a point where the country would lose ~85% of its population every two generations. That's an extreme example, almost to the point of absurdity, but even so it sort of illustrates the problem. To support the ever increasing number of old people, policy makers can either A) Accept much higher levels of immigration (unpopular) or B) Increase the tax burden on the fewer and fewer working young people (which will probably decrease fertility even further). Even if we assume option C exists (no immigration but replace all workers with robots) you're still looking at a situation in many countries where the actual human population of the country is reduced by >90% within one human lifetime. While countries like the U.S. won't be hit quite as hard by this, the trends are pretty clear. Younger generations are having a fraction of the number of kids older generations had[2] and this trend will continue to accelerate in the near term. [1]https://www.insider.com/south-korea-birth-rate-abandoned-schools-photos-2021-7#south-koreas-fertility-rate-has-been-in-free-fall-for-years-and-the-country-no-longer-has-enough-children-to-fill-its-schools-1 https://www.insider.com/south-korea-birth-rate-abandoned-sch... [2]https://i2.wp.com/www.brookings.edu/wp-content/uploads/2021/05/kearneylevine_fertilityrate_fig1-01.png https://i2.wp.com/www.brookings.edu/wp-content/uploads/2021/...