[oxff]

First developed country to enact anti anti-natalist policies (restricting birth control, strengthening marriage etc) to win; or you could just drive off the fertility cliff like lemmings with females all working or in edu until 45+.

[int_19h]

It'd likely have to combine all that with exit visas.

[Thorrez]

Vatican City?

[tsimionescu]

While the parent commenter is obviously bigoted and being absurd, Vatican City is not a good example, as all citizens must be members of the church, and the majority of those have to take vows of celibacy.