For me it is China after I noticed that a lot of them uses some kind of strange client that always shows that they have 0 progress to get better priority from other pears. Later after I started to look into it I noticed that they do not even seed.
And then eventually all the Chinese beers will get vpns or whatever to mask their ip and country of origin, thereby defeating the whole purpose and creating more cpu usage to lookup the blocks for every connection... if it's very dumb things to do, it doesn't solve the problem at hand. I don't know how to solve it but one day there will be a client that someone will make that will.