One of the points about demographics that's been really haunting me lately is the nonsubstitutableness of births. In other words births of human beings is not a

One of the points about demographics that's been really haunting me lately is the nonsubstitutableness of births. In other words births of human beings is not a commodity that you can "catch up on" in any generational sense. Generational cohorts are made in fixed time, and when made late will lag with an offset that can never be backfilled later on. We can only produce infants, never the 8 year old who was never born to fill the gap of missing 8 year olds from folks who couldn't be bothered or weren't ready to have children 8 years ago. Likewise for the absent 20 year olds and so on and so forth. We cannot correct after the fact to rebalance our population pyramids from being so top heavy. There is a huge commitment either way, and that commitment/choice is irreversible. One commits to new life or for voids of life, both are not without consequence. One other interesting thing to this is to watch the shifting median ages of populations. > China's median age was 22 in 1980. By 2018, it was 40. That will rise to 46 in 2030 and 56 in 2050. In the US, the median age was 30 in 1980 and 38 in 2018. In 2030, it will be 40, and 44 in 2050. India, by comparison, had a median age of 20 in 1980 and 28 in 2018. https://www.scmp.com/comment/insight-opinion/asia/article/2180421/worse-japan-how-chinas-looming-demographic-crisis-will https://www.scmp.com/comment/insight-opinion/asia/article/21... That's always been fascinating to me to think of an entire graying population and of all those civilizations of past eras who are no more. You can get a distinct taste of that gravity by thinking of an entire genetic pool shrinking in our lifetimes.