If birth rates are as much a cause for concern as many people seem to think, and we absolutely need to solve it (instead of solving, for instance, the fact that the economy purportedly requires exponential population growth forever), perhaps we should hope that AGI comes soon.
I am worried about what will happen to various nations' economies relatively soon, long before the population actually halves, but I'm not worried that the fertility rate would continue on its trend as demographics change. Ignoring the potential second-order effects of economic collapse, wars over resources, etc., I think fertility rate would stabilize given that culture and genetics would by definition quickly become dominated by the people who do reproduce.
