Greentext

Even the fears about the economy and government spending are bullshit. Notice the folks obsessing over birthrates always quote the retiree to worker ratio. They don't talk about the dependent to worker ratio, and that's what really matters. Yes, our populations are aging, and yes that means relatively more old people to take care of. But we in turn also have far fewer children to take care of. If we can adapt to the Baby Boom era, we can adapt to an aging population.

Further afield, fears about human extinction are total bullshit. No country is a monolith; every nation has groups within it with higher and lower relative birth rates. If the birth rate stays low and never recovers among the mainstream society, eventually the smaller groups end up composing most of the population, and then the birth rate recovers. The Amish inherit the Earth.

Or, if even that fails, ultimately technology loss alone stabilizes your birthrates. Eventually your population falls so low that you just can't physically manufacture reliable birth control anymore. That's a product of industrial production. It requires a certain minimum population size to run a factory. Below that and we just regress to earlier technological eras. Eventually we end up back in a mostly agrarian state, and suddenly having kids is once again economically beneficial.