rtaylor777
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Re:Chess Rating vs. Expected Results - 2007/03/21 23:09
From the wikipedia site
http://en.wikipedia.org/wiki/ELO_rating_system
Élő's system was adopted by FIDE in 1970
The phrase "ELO rating" is often used to mean a player's chess rating as calculated by FIDE. However, this usage is confusing and often misleading, because Élő's general ideas have been adopted by many different organizations, including the USCF (before FIDE), the Internet Chess Club (ICC), Yahoo! Games, and the now defunct Professional Chess Association (PCA).
The real difference in the ratings between different organizations is not so much due to significant differences in the statistical formula being used but that each one's rating is only valid for the statistical data that the organization doing the rating has. So a FIDE rating for one user only has real comparative value when compared with the FIDE rating of another user. The USCF rating for one user only has real comparative value when compared with the USCF rating of another user.
Some effort has been made to compare users across rating systems using performance of a number of users who have been rated in both systems. This is how statistically it is possible to say that a persons USCF rating is X amount higher or lower than their comparative FIDE rating would be. It is all just comparison between players results in a particular performance database.
So as a result there is no hard and fast rule that says a person with a certain rating is capable of this or that specifically it is just valid for evaluating comparative strengths between individuals who have been rated in that particular rating system.
So how did a particular rating get assigned to the first rated players?
http://chess.about.com/od/chessratings/ss/aa07b17_3.htm
Already in 1959, the USCF rating system arbitrarily used 2000 as the upper level for strong club players and 200 point divisions to assign players to classes. Elo kept these measures because they were 'steeped in tradition'.
So compared to these first specifically assigned players everyone who got rated was compared to these specific players and given a comparative rating. Now there has been a lot of drift of the ratings due to the nature of statistics and as a result you will hear talk of deflation of ratings and measures used to try and compensate.
There have been some efforts to estimate the rating of players that were never rated in an existing system. This would be a historical rating system. See this page...
http://members.shaw.ca/edo1/
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but I thought I had read that this ELO rating system only had hystorical meaning and nowadays FIDE-rating was being used 