Quick and Dirty Rating System

While the discussion of Swiss Pairings is almost guaranteed to create a fight at any chess tournament, the discussion of chess ratings will almost certainly generate a massive outbreak of cluelessness. Why? I'll discuss that another time. But chess ratings are important, and handled correctly provide an excellent tool for keeping players enthusiastic about their chess.
For the junior chess club I run I use quick and simple rating system that can be used in any stand alone chess club or coaching group. However, it isn't my invention, as the credit rightly belongs to the US Chess Federation. The system I use is described in their Guide to Scholastic Chess.
At the Gungahlin Junior Chess Club I start every player off with a rating of 500. Then simply for each game the winners rating goes up by 25+(Lr-Wr)*0.1 eg 25 points for a win plus 10% of the difference between the players. If a 600 player beats a 500 player the winner gets 25+(500-600)*0.1 or 15 points. The losers rating goes down by the same amount. The ratings changes are limited to 0 and 50 points which can occur if the ratings differences between the players exceed 250 points. In the case of a draw there is no winning bonus and the rating change is simply (Or-Pr)*0.1 where Or = Opponents Rating and Pr = Players Rating.
Although the system can be applied on a game by game basis, I usually apply it across a tournament, by calculating the changes using the rating at the start of the tournament for all players, and applying the changes at the end of the event.
While it is simple to use it does have a couple of drawbacks. The winning bonus of 25 is possibly too high, causing ratings to jump around. Reducing it to 20 maybe more sensible. Secondly, I would not regard it as accurate as the Glicko System. This is hardly surprising as Glicko is the product of serious statistical analysis, while this system is designed for ease of use.
There are a couple of possible modifications. Peter Simpson, who organises the Tuggeranong Junior Chess Club, independently developed a similar system a number of years ago. In his system the win bonus is 20 points. If the ratings difference between the two players is < 100 points then the modifier is 1 points for every 10 points of the difference. However if the difference is between 100 and 200 the the modifier is 10+1 point for every 20 points of difference above 100. And above that the modifier is 3 points (or 37 points for an upset) for a difference between 200 and 250, 2 points between 250 and 300, and 1 point above that.
So if a player rated 685 beat a player rated 500, the winner would get 5 points and the loser would drop 5 points. Of course if the result went the other way the winner would gain 35 points.
So if you are thinking of setting up a ranking system in your club or coaching group, then either system should do the trick. As the number of games played at the GJCC increases, I'll report back on any interesting findings.