User blog comment:Commander Marko/How 'screwy' the League System is/@comment-5557556-20130928111526/@comment-15244341-20130928132141

That is the MMR. I thought that was pretty much common knowledge. You Match Making Rating depends not on your actual League, but rather on your win/loss ratio and most likely other stuff.

Imagine a guy that gets placed in bronze, wins every game because he is a Platinum-level player but never manages to make his promotion for whatever reason. He could be in bronze forever, but he will never be placed in matches against lower bronze players because his MMR is much better than theirs. This is obviously an exaggeration, but the point should be clearly conveyed.

You don't get placed with people in the same league as you, you get placed with people with the same or closer MMR to yours. That means that bad gold players might constantly be placed with silver players rather than with other better gold players.