Myrmecia, Yes. I remembered some 60,000 stat, but vaguely. Since, I looked, but couldn't find it. 64,000 foreign adults enter the NIH each month. Perhaps that was the source? The point isn't the exact #. But my larger point.
Does it improve Korea to grow its foreign population? In terms of Muslim immigrants, (about which you commented), two more Muslims just shot at a free speech contest in the US. This on the heels of the Charlie Hebdo cartoonist shooting in France.
Also, cultural diversity means you are bringing in people that do poorer in education. If that isn't a terrible negative, you make it one when you adopt the western multicultural model wherein all differences in achievement PROVE the majority culture is racist.
Korea has a right to choose if it wants to follow the West towards increasing immigration and using multiculturalism to (supposedly) lessen tensions or stick with what it has been largely doing for the past 5,000 years: using culturist 'Hermit Kingdom' policies to stay Korean.
This is a huge and irreversible decision. It needs debate.