Comment by andsoitis
>> But then you get an aging population and all the problems that that brings with it.
> Only for a generation (mostly \s but entirely true).
That's not accurate. The problems of population aging are not confined to a single generation. They are structural and persistent, unless the underlying institutions adapt.
Aging is a continuing demographic process, not a single event. Once a society enters sustained low fertility and longer life expectancy, each cohort is smaller than the one before it. Each cohort also lives longer. That means that today's workers support more retirees. Tomorrow's workers will support even more, unless something changes.
It can feel (but isn't) like a single generation problem if major structural changes happen like: raising retirement age in line with life expectancy, shifting pensions to funded, large-scale immigration, major productivity gains from technology, or cultural shifts to high fertility.
> Once a society enters sustained low fertility and longer life expectancy, each cohort is smaller than the one before it.
I mean, unless fertility completely collapses (to like less than 0.5) then it'll mostly be a single generation problem. Regardless of any future changes, the current generation (my kids etc) will be supporting a much larger older cohort, with problems arising from that. I am one of 4 siblings, have two kids, and as long as both of them have two kids, no more problems arise (obviously extrapolating to the population).
There's some amount of irreducible demand for kids so I'd be surprised to see TFR continue to decline on a generational basis. Mind you, I could be wrong (or alternatively, we could see a massive increase in TFR like we did post WW2).