Remember when we were younger and the world's population hit 7 billion, everyone was really, really concerned about overpopulation??? I even did not want to have any kids because of this.
Now, Korea is seriously going to be worse than even Japan. And faster too.
Back in Jamaica one of my grandma had 7 children, the other one had 8 (with 2 stillborn). Now most women there have 1 child.
Here in Thailand today, we see much of the same thing. Talking to people they report their grandparents having 4-8 kids. Now most Thai women are lucky to have even one child. Same in Vietnam and Indonesia, which I frequent regularly too.
An outlier is when I was in Qatar recently, it was very common to see large (3-7 kids) families everywhere from all over the Middle East.
It is what it is.