This is indeed the leading theory about where the world will be heading over the next couple of decades. But I think the answer really depends on the culture of

This is indeed the leading theory about where the world will be heading over the next couple of decades. But I think the answer really depends on the culture of subpopulations. In the USA for example, republican ruled states have more babies than democrat ruled states [1]. Or in israel, the fertility rate of the orthodox haredi minority is very high with 6.9 children per woman in 2017 (children not childbirths) compared to the non-haredi per-woman value of 2.4 [2]. So where will this lead us to? I think we'll experience growing percentages of conservatives/orthodox populations across the world while the liberal populations will shrink. Overall there will be a shrinkage but the conservative population growth might eat up that shrinkage and one day we might have overall growth again. But predicting the future is hard of course. For example, you could have the conversion of the conservative mindset towards liberalism which is happening in the entire world since maybe 100 years or such eat up every population increase of the conservative minorities. Or you could have sci-fi tech that influences population infertility quite much, e.g. with artificial uteruses. With them, minorities that value large amounts of children might grow quicker and governments could want to influence how many children are being grown to fight population declines. Or it might be figured out how to prevent/reverse aging and the number of "natural" deaths will sink to zero. Then your population will start growing again even without the contribution from conservative/orthodox minorities as the number of babies would still be larger than the (low) number of deaths due to accidents, crimes, etc. [1]: https://www.fatherly.com/health-science/republicans-have-more-children/ https://www.fatherly.com/health-science/republicans-have-mor... [2]: https://en.idi.org.il/articles/20439 https://en.idi.org.il/articles/20439