[Nothingburger]

I don’t have the numbers in front of me, but check Wikipedia.

Korea is an extreme case with the dominance of Kim as a surname — something like a quarter of the population. Ditto for Nguyen in Vietnam.

China is more varied but you still have a disproportionate share of people named Li, Chang, Wang, Liu etc.

Japan has something like 100,000 surnames in use, but again you’re dealing with a lot of people named Sato, Saito, Watanabe, etc. But Japan is still rather diverse compared with China or Korea.

Conversely, in the West, some countries are wonderfully varied. Take, for instance, Italy, where you could often tell from someone’s surname what town or village they were from. With population shifts — poor south to industrial north — this is no longer as extreme. But to this day, I guarantee you that the top 50 surnames in Torino won’t look much like the top 50 surnames in Palermo.

[Albion Wilde]

I agree about Italy. It is a very ingrained cutural habit. I lived among Italian-Americans for a long time; they would identify people by what street corner they were from. After two decades, they were still telling me I was not a "real" member of "da neighborhood."

In Italy itself, they have a term called campanilismo. It's an idiom that means to rarely venture farther than the sound of one's own parish church bells.