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…
Miscarriages are not births. If the birth rate remains at 2.1 you can have as many miscarriages as you want, and the population will still increase. The same with Hikkikomori, and gay people. As long as there is 2.1 children born for every woman, then the population will increase. The only factor which you mention that is correct is that in a society that murders female babies, then yes, you will need more than a 2.1…
2.1 children per woman is the REPLACEMENT rate, meaning this is what it would take for the population size to remain roughly the same. One kid to replace her, one kid to replace a random dude (not necessarily the father!), and .1 kids to make up for the kids that die before they reach adulthood.
This does not mean that every woman needs to have children. it means that the total number of children divided by the total amount of women needs to be 2.1 for the population to remain stable