2.1 children per woman. That is roughly considered replacement level fertility for a given population.  These days, most advanced economies have total fertility rates lower than that. And some of the lowest fertility rates can be observed in Asia. Like in Japan, South Korea  and Singapore where the rate was 1.14 in 2019. 

Assistant Professor Tan Poh Lin from the Lee Kuan Yew School of Public Policy has called this a crisis " of national importance." And one that will be around for a long time. An expert in population research, she has studied what can be done to reverse this demographic decline.  and has some interesting findings on what works — and what doesn't.