--> Turn 7 it was pretty much clear that he had East China and Indonesia and only West China to expand into. In the following turns he didn't show you his full income so it was clear that he was expanding. You could have finished him off safer and faster.
Here is an interesting long ladder game. I recommend analyzing this game closely since it's kind of a tutorial where a top tier player (orange color) shows how to reach number 1 ladder spot:http://warlight.net/MultiPlayer?GameID=5616037