Árpád E. Élő (b. August 25, 1903 in Hungary - died November 5, 1992 in Wisconsin) is the creator of the ELO rating system. He spelled his own name "Elo" after he left Hungary, a common anglicization.

Elo was a professor of physics at Marquette University in Milwaukee, Wisconsin. He was a chess master who won the Wisconsin State Championship many times.

Elo is best known for his system of rating chess players. The original chess rating system was developed in 1950 by Kenneth Harkness, the Business Manager of the United States Chess Federation. By 1960, using the data developed through the Harkness Rating System, Elo developed his own formula which had a sound statistical basis and constituted an improvement on the Harkness System. The new rating system was approved and passed at a meeting of the United States Chess Federation in St. Louis in 1960.

The first USCF rating statistican was Bill Goichberg. Goichberg often disagreed with Elo on details about how the system would be implemented.

In 1970, FIDE, the World Chess Federation, agreed to adopt the Elo Rating System. From then on until the mid-1980s, Elo himself made the rating calculations. At the time, the computational task was relatively easy because less than 2000 players were rated by FIDE.

Goichberg later demonstrated that Elo was giving US players lower ratings than they deserved. This matter was debated at the FIDE Congress in Buenos Aires in 1978. The FIDE Congress voted to give Bill Goichberg and Michael Valvo among others an increase in the ratings, based on their arguments.

FIDE reassigned the task of managing and computing the ratings to others, excluding Elo. FIDE also added new "Qualification for Rating" rules to its handbook awarding arbitrary ratings (typically in the 2200 range, which is the low end for a Chess Master) for players who scored at least 50% in the games he played at selected events, such as named Chess Olympiads. See [1] and [2]. Elo and others have objected to these new rules as arbitrary and politically-driven.

Books

• The Rating of Chessplayers, Past and Present (1978) ISBN 0668047216