zlacker

I 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

>>johngo+(OP)
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.

>>varjag+Tp
We do. It's called "urbanization".

Large cities are inherently inimical to living in large families. And yes, it was apparently the case even in the Roman Empire.

>>cybera+k42
Decline happens also in territories that had been urbanized decades or even centuries ago but had positive fertility rate until 2010s. As I said you can pull a patchy blanket of micro-theories explaining each region but not one theory that accounts for them all.

>>varjag+Si3
Yes, but it happened in stages. The fertility fell each time people moved into higher density areas.

You can even see mild recovery when de-densification happens. It's very interesting to compare the fertility rate in Denmark and Netherlands:

https://www.macrotrends.net/datasets/global-metrics/countrie...

https://www.macrotrends.net/datasets/global-metrics/countrie...

You can see the dip and a recovery in Denmark and essentially no recovery in Netherlands (until post 2000, but that was due to immigration). Why?

Here's the answer:

https://www.macrotrends.net/datasets/global-metrics/cities/2...

https://www.macrotrends.net/global-metrics/cities/21930/amst...

Denmark de-densified its cities during the late 70-s (that's why Copenhagen is the world's most liveable city, btw).

>>cybera+cv5
Generally when people say urbanisation is the cause of fertility decline they mean people moving out of 7 child families at subsistence farms and rice paddies to city factories. Not any developments in Denmark or the Netherlands in last 150 years.