It is HYPOTHESIS that the massive decline in childbearing is due, or even primarily due, to fewer childhood deaths. I think you should make a better case for that, rather than just proclaiming it.
This supports it somewhat. However, the statistical analysis is missing, and use of "mean", rather than mode, seems suspicious:
http://www.cia.gov/the-world-factbook/field/mothers-mean-age-at-first-birth/
I personally suspect (but don't claim to be able to prove) that accidental/incidental chemical sterilization is a significant factor. You'd think some PhD candidate would take that as a thesis and would like to rule that out.
There seems to be very little real science, or even good backing statistics, to make such a a simple case that psychology + birth control explains the plunge we have seen since the 1960s. Maybe. Maybe not. Quantifying accidental chemical sterilzation, and maybe some other possible factors, SHOULD have been done a long time ago.
There is good evidence that sperm motility in the West is low. Although that is only one possible factor, I doubt that is an issue of "psychology" nor "birth control".
You'd think some decent scientific questioning would have been done long before now. But it seems, to me, oddly missing.
Monsanto wouldn't like that study, I am sure. Nor would lots of other players.
Post mRNA I know we can explain any further drop in reproduction as just "fear of Covid coming back" and "fear of climate change". But that's not science, either. I fully expect emotional "heartbreak" to be the favorite theory explaining any unusual surge in all cause mortality in the coming years. We won't need to question that because our Masters and Talking Heads will have already predetermined it to be Truth.
In all seriousness, I would expect extraordinarily high divorce rates + LACK OF MARRIAGE to be vastly more significant psychological factors than declines in childhood mortality. But that isn't being analysed, either.
As I think about it, the psychological factor of parents having fewer children because they expect fewer of their existing children to die seems laughably implausible. How many parents go "Oh! We just buried Tommy! Lets have more sex so we can replace him!"