There was optimism - the hope of a better future - in 1950, 1960, and 1990. There isn't now.

We are in fact in a better place than we were then. But we don't trust the derivative.

Right so it seems like the state of the economy has literally no effect if the birth rate was extremely high at both times of economic hardship and prosperity.

I mean 50-60 was the post war baby boom, so not really sure if that's a good example for the US in particular.