The distribution of the rating of all players looks a bit peculiar. Also, the number of problems correctly solved by <35% (but still rated 1500ish!) seems to increase.
there are some stalemate game can increase the rating to both player,that is why the 1500 above player getting increase
Yes, I think a lot of problems still are "under rated" (if that is the proper expression?).
The distribution of the rating of all players looks a bit peculiar. Also, the number of problems correctly solved by <35% (but still rated 1500ish!) seems to increase.