I think you mean more western cultures.
And its not a decline, its just that other places in the world have finally started to ge their shit together in regards to ecenomic and scientific growth (hopefully human rights and higher living standards will follow aswell).
Family sizes are dropping worldwide anyway from what I understand. China for example has significant demographic issues and they've already dropped their projected growth from 10% to around 7.5% (going off memory here) for each year of their current 5 year ecenomic plan.
So the voracious growth that some countries are having wont last forever just like it didn't in the west.







