alt Hacker NewsI doubt this explains the world-wide phenomenon, but regionally sure. I remember in the 90s when studies brought the Nigerian population estimates down this triggered a drop of growth forecasts across sub-Saharan Africa.
Edit: changed world-wife (which sounds interesting demographically) to world-wide
Sure, it is quite far-fetched. However it is extremely uncommon that we experience unified social trends all across the board, from liberal Finland or Japan to North Korea and Taliban-run Afghanistan. Usually there are odd reversals and exceptions here and there; not this time apparently. And we still lack a satisfying theory that could account for fertility decline in every country.