Becoming a Professional Player in Korea
I just found this nice article: Becoming a Professional Player in Korea
The title is self-explanatory. I was impressed with the number of Korean insei at any given time: 168! That is more than 3 times the number of insei in Japan, at least at the time when I was insei.
By the way, the article is part of a nice series of Korean lessons.
In the “Proverbs Part (2)” one, I found a quite funny comment in the “If You Have Lost All Four Corners, Resign” section:
“However, after many brilliant professionals in Korea discovered the value of the sides and the center, the modern version of this proverb goes like this: “If you have secured the four corners, resign.”
The funny thing is that I have known the updated proverb from Japanese sources for a very long time now, so the brilliant professionals in Japan must have discovered that before the brilliant professionals in Korea 
February 13th, 2007 at 10:24 am
Given how large the population in China is, I can’t help but wonder how many “insei” they are cultivating - even if these are in less-formalized schools.
It’s odd that the proverb about the four corners seems to have only been recently refuted in Korea. Takemiya Masaki had long proven that you can lose all four corners and make one massive territory in the center. Much of his insight is captured in the English title, “The Imagination of a Go Master”.
If I recall correctly, Cho Chikun did the same in one game (although he probably lost only three corners - completely).