One aspect this article does not address at all is the massive sex ratio imbalance in India and China (for different reasons) at around 1,100 men for every 1000 women. This means there are 100 million girls less today in these countries alone, finding a suitable partner becomes harder and there are lesser number of couples will be there in the first place who can have kids The 2.1 replacement is perhaps not adequate…
Now that fetal sex selection is a thing, the previously fixed relationship between TFR and RR is fixed no longer.