A very complex issue. China had tried with 1 child norm from 1979 to 2015 but changed its policy to 2 child norm. Since 2021, it is 3 child norm, because of ageing population (higher life expectancy) & skewed sex ratio, more males than females. India the birth rate today is about 1.9 -

And in many countries like Japan and Korea it’s negative growth.

Yes, due to urbanisation & many more distractions, people are marring late & do not wish to have too many children perhaps 1 child is the norm. India Birthrate per 1000 1950: 44.18 2000: 27.52 2025: 16.55 Life Expectancy: 1950: 35 years 2022: 70 years. Lower birthrate & higher life expectancy.