One Degree wrote:
I think it may be student debt. If you put people in debt right away, it reduces their urge to reproduce. Debt seems to be the main difference in ‘developed’ countries from undeveloped.
Can't be student debt, as in most European countries tertiary education is free and they have some of the lowest birth rates. I don't think most young people in Europe have any debt, but if they do it's most likely a mortgage. Overall, I don't buy the idea that people don't have enough money or too much debt to have kids. In developed countries it's the poorest who have the highest birth rates after all (although in some countries they may be second to the very, very rich).
My very speculative theory is that there's always a part of the population which was susceptible to opt out of reproducing or to have only one child if given the opportunity, but this was never an issue because not reproducing was socially unacceptable or very difficult before highly reliable contraception became available. Right now that group is in the process of reducing their share in the population at which point we'll bounce back (just like the rabbits ) because there will be a higher share of people who are predisposed to have more kids.