[fiblye]

>Children are massively expensive, especially to the parents. Parents, especially those who work, can't be "compensated" for the work, costs and risks of raising children. The motivation to raise children is entirely irrational from the perspective of the individual.

So, essentially, no reasonable person would have children. Instead we should have an underclass of people who were, in your words, "irrational" enough to have children to move to another country to work for very low wages and serve and literally change the diapers of the aging, enlightened elite who were rational enough to not have children.

Raising birth rates to a sustainable level is a long term investment and stable solution. Mass immigration just kicks the can down the road. And currently, only two neighboring countries have birth rates above replacement rates: Indonesia and the Philippines. Their birth rates will likely drop below the replacement rate by 2050, in which case mass immigration from those countries to other countries deprives them of a stable future and royally screws countries who were dependent on immigrants who will no longer exist.

[bayesian_horse]

Nothing wrong with a solidly irrational motivation. The desire to become parents seems to be a neuro-biological thing, influenced by genetics, random stuff and psychological factors.

I don't believe that getting children for the greater good is a massive thing.

And again, there still is no proven way to increase birth rates short of authoritarian measures.