No, there's no accounting for that, but due to the way the system works, if a region does become stronger it will eventually start to show in the ratings. I have noticed the same thing you noticed. I wouldn't term it "bias," as a statistics teacher "bias" usually indicates to me some flaw that's giving false results. I would hope that maybe it's reflective of a real difference, and not a flaw. Also, sometimes it can appear that way, but one region just has a wider range of ratings than another, so the region has more of the top teams AND more of the bottom teams.