alt Hacker NewsIt's most societies, period. Of the 237 nations and territories recognized by UN, only 42% had a sustainable fertility rate. [1]
It seems reasonable to assume kids having more positive economic power in the past played a significant role, but there's counter-examples abounds in modern times. Nigeria is heavily urbanized yet has one of the highest fertility rates in the world. Or on the other end of the spectrum, Thailand has a very large chunk of people living off farming, yet has one of the lowest fertility rates in the world.
[1] - https://en.wikipedia.org/wiki/List_of_countries_by_total_fer...
What's a "sustainable" fertility rate to you? Given that the current human biomass is completely unprecedented in all of history and is only made possible by artificial energy inputs (fossil fuels and ammonia/fertilizer), I posit that the only sustainable fertility rate is well below 2.0