Patrick Boyle has looked at causes of decline in the total fertility rate around the world and concluded reduction in the formation of couples (married or not) is a major cause.
replies(2):
https://www.ggd.world/p/the-global-collapse-of-coupling-and
I wonder if the ultimate cost (in lives never born) of technologies like smartphones and Tinder will be. If a significant part of the entire youth cohort never learns to interact with the other sex in the real world, we might be looking at a pandemics of loneliness - and at subsequent global birth deficits in eight to nine figures.
If coupling is reduced, it should become the norm for women to have and raise children alone, or at least without a male partner. This increases the burden on women, so at the same time the number of children they must support would have to decrease.
This could be achieved technologically, by filtering sperm to remove Y chromosome carrying gametes. As a result, the female/male ratio of newborns would dramatically increase. At the US TFR of 1.66, a 2:1 female to male ratio would be more than enough to maintain the population. Even higher ratios could be imagined, leading to an almost entirely female population.
Social engineering to reach this state is left as an exercise to the science fiction writer.
Raising children is a lot of work. It’s twice as much work without a partner, not to mention not having the extra income. (I don’t imagine men in a 2:1 society will be interested in paying much child support.)
The number of children in advanced societies (particularly in cities) has already plummeted. And I don’t think many women are going to want to sign up to be single mums.
As far as sperm selection goes… that’s already an option popular in China and India, along with sex selective abortions. The preference is for males, though, for various reasons. I am not convinced the end result of this is wholesome.