This appears applicable to whites in the west and Asians in east Asia. I'm not so sure this is universally true. You see big differences in fertility rates in different ethnic groups in the US.

And it may not even generally be true. It might just be how things appear right now given current circumstances. If you cut off immigration to the US, which is driving growth, I doubt the white fertility rate would stay at or below replacement. Wages for low skill labor would rise and fertility would go up. Who knows what the birth rate in Japan would be if their economic policy were not so incompetent.