Arpad Imre Elo, born 25 August 1903, developed the Elo Rating System in 1959 at the request of the US Chess Federation. The Elo Rating System was adopted by the World Chess Federation (FIDE) in 1970. Later (date needed), the USCF modified the Elo rating system to use a slightly different model for the variability in a player's performance substituting one based upon the logistic distribution in place of Elo's selected normal distribution.
In 1978, Elo published The Rating of Chessplayers, Past and Present, a book describing his system and presenting ratings for 476 of the world's strongest chessplayers.
Often people who are not familiar with the nature and limitations of statistical methods tend to expect too much of the rating system. Ratings provide merely a comparison of performances, no more and no less. The measurement of the performance of an individual is always made relative to the performance of his competitors and both the performance of the player and of his opponents are subject to much the same random fluctuations. The measurement of the rating of an individual might well be compared with the measurement of the position of a cork bobbing up and down on the surface of agitated water with a yard stick tied to a rope and which is swaying in the wind. -- Arpad Elo, Chess Life, 1962