Amazingly enough, my Bachelor's thesis was on this very subject -- rating systems. The internet chess club rating system is, or at least was, based on my work. See http://rangevoting.org/WarrenSmithPages/homepage/works.html paper #20 and paper #88. Paper 20 discusses among other things, a "fluid dynamics" model of learning as reflected in ratings, and discusses the rating distribution, and how to optimize rating system parameters. The rating distribution has features of a "extreme value distribution." Paper 88 discusses a new approach. Glickman kind of annoyed me by a combination of ignoring and appropriating my work, which I told him all about before he got going on the topic. But I do not know what Glickman's latest stuff is, haven't looked at this in years.