The Glicko rating system and Glicko-2 rating system are methods for assessing a player's strength in games of skill, such as chess and go.
http://chess.com/blog/kurtgodden/elo-to-glicko-your-rating-explained
(I don't mind linking to that site when their content is of high quality!)
http://chess.com/blog/kurtgodden/elo-to-glicko-your-rating-explained
(I don't mind linking to that site when their content is of high quality!)