Roughly a quarter of the world's people live in China.

I think it's not a quarter, it's more like a fifth.

i think they want to learn kung-fu.

nope. its actually one third. there is around 6.23 billion people in the world and there are 2 billion people in china.

Um, No. There are currently 1.34 billion people in China as I'm writing this. There are 6.84 Billion people in the world. Therefore 134/6.84 = .196 aka roughly 20% or one-fifth. Who's the idiot that said 2 billion? Fact check people. Do a little research.