I've solved it, in theory.
And one day I will move to theory and live happily ever after, and have many children.
I was reading the slides of the UPenn course called The Demographic Future of Humanity: Facts and Consequences and an idea came to me.
Tbh, i don't think it's a very good idea, but it is at least an original idea, to be kept as our species' last resort, so to speak.
On this sub, most people discuss how to raise TFR, but what it there was another way to approach the problem. It came to me when I saw the formula for the replacement rate :
Replacement rate ≈
(1 + sex ratio at birth) /
Probability of a woman to survive to 30
Note that this formula is very gender specific.
Here's the biggie : raising TFR above replacement ratr is hard, and nothing we've tried so far has worked. But what if we could lower the replacement rate, and meet the other metric half-way ? Let's say, 1.8 - which I believe, with the proper will, and the proper means, can be done.
But since nearly all countries in the world have a probability if a woman to survive to 30 maxed out, with perhaps very low income countries being a few percent behind, there's only one variable that is left to change: sex ratio at birth.
Sex ratio at birth is about 105/100 male to female, with slight variations which i haven't really managed to understand yet. It's a feature of the species. But what if it were two females to a male? The sex ratio would be 100/200 -> 0.5
The replacement rate would become (1 + 0.5) /0.95-ish which is something like 1.57 birth per woman.
Obviously, this is all very theoritical. I'm not suggesting to abort half the male embryos. And I'm not trying to bring about a polygamous utopia. I'm thinking in theory. The technology to modify the birth ratio within our genes doesn't and shouldn't exist.
But what about IVF treatments? In some countries today, they account for 10% of all births. And those embryos / eggs are screened for quality. Selecting only those with XX chromosomes wouldn't be much more work.
Let's make the calculation with 10% female only IVF-originated births : sex ratio becomes 0.81 (out of 100 births, 10 ivf-originated females, 45 natural females, 45 males, to 55 females), and replacement rate becomes 1.9, a decrease of 0.2
Ok, it's not much, but it is that much better.
Note that there aren't more births in this scenario, merely the amount of children per woman necessary to sustain a population goes down.
So how does it help? Well, it won't, realistically. But in theory, it could, if the following assumptions are correct:
- Men struggle to find wives more than women struggle to find husbands, therefore increasing the supply of women in a country would increase the supply of women willing to make the sacrifices inherent to pregnancy and motherhood.
- The size of the population doesn't matter, the structural integrity of the age pyramid does.
If those are correct, then the proportion of childless women at 40, who seem to be about 30% in our modern developped economies, might stay the same, but the number of childless men might decrease as opportunities increase to find a wife.
Let's imagine now that IVF becomes free and normalized, at the condition that the baby be female, and that 30% of all births are made this way, which i reckon to be possible.
Sex ratio becomes 0.54 (out of 100 births, 30 are females from ivf, 35 are female natural, 35 are male)
The replacement rate goes down to 1.62. Not that unatteinable now, is it?
But, it's all very theoretical.