There’s a (positive or negative) correlation between birth rates and dozens of factors, because over the period birth rates have been falling, the world has changed dramatically. Issue is we don’t know what is causal. education also correlates with all kinds of other factors like income, type of work, marital status, and political views, meaning birth rates are also likely correlated with all of these factors.

>Issue is we don’t know what is causal.

Is it really true that this is not known? Although I only claimed correlation (and am thus surprised that I was downvoted twice, as that claim is obviously true), based on the famous "robustness" of this observation, I strongly suspect that confounding factors like those you mention have already been analysed to death, and found not to eliminate the explanatory power of women's education.

At least, checking these confounders seems an obviously valuable and interesting avenue to explore. If it hasn't been done yet, I wonder what social scientists are doing instead.

> I strongly suspect that confounding factors like those you mention have already been analysed to death

I doubt it, because the xUSSR is an obvious counterexample.

Access to condoms is probably a bigger factor.

I agree that access to birth control is a strong factor and likely heavily confounded with women's education. I think there will have been examples of women's education but lack of birth control (e.g., predominantly Catholic nations, especially early on), not sure if there are many examples in the other direction though.

Unfamiliar with USSR -- is the birth rate high there despite lots of educated women?