Chessmetrics is a system for rating

chess Chess is a board game for two players, called White and Black, each controlling an army of chess pieces in their color, with the objective to checkmate the opponent's king. It is sometimes called international chess or Western chess to dist ...

players devised by Jeff Sonas. It is intended as an improvement over the

Elo rating system The Elo rating system is a method for calculating the relative skill levels of players in zero-sum games such as chess. It is named after its creator Arpad Elo, a Hungarian-American physics professor. The Elo system was invented as an improved ...

Implementation

Chessmetrics is a

weighted average The weighted arithmetic mean is similar to an ordinary arithmetic mean (the most common type of average), except that instead of each of the data points contributing equally to the final average, some data points contribute more than others. The ...

of past performance. The score considers a player's win percentage against other players weighted by the ratings of the other players and the time elapsed since the match. A 10% increase in performance is equivalent to an increase of 85 rating points. The weighting of previous matches digresses linearly from 100% for just-finished matches to zero for matches conducted more than two years ago.

Formulas

Performance rating adjustment after tournament: :

Performance Rating = Average Opponents' Rating +  PctScore - 0.50) * 850/code>

Weighting of past tournaments (age in months):
:100% * (24 - age)

 Criticism


In 2006 economists Charles C. Moul and John V. C. Nye  used Chessmetrics to determine the "expected" results of games, and wrote:Ratings in chess that make use of rigorous statistics to produce good estimates of relative player strength are now relatively common, but comparing ratings across different time periods is often complicated by idiosyncratic changes (cf. Elo, 1968 for the pioneering discussion). Sonas uses the same rating formula throughout our sample and updates this rating monthly instead of annually, as is more common. Moreover, retrospective grading allows him to establish rankings that are unbiased estimates of the "true" relative strengths of players.

The system has also been described as "the most complete and resounding attempt made to determine the best chess player in history". However, the system is more accurate in measuring a player's success in competition than quality of play.Computer Analysis of World Chess Champions
 M.Guid and I.Bratko,  ICGA Journal (Vol 29, No. 2, June 2006, pages 65–73).

 Popularity

The original article on Chessmetrics was published in  Chessbase in October 2002. Since then, Chessmetrics has become reasonably well known and features numerous articles in  Chessbase and The Week in Chess 



''The Week in Chess'' (TWIC) is a chess news web site. It was founded in 1994 and is based in the United Kingdom.

''TWIC'' has been edited by Mark Crowther since its inception in 1994. It began as a weekly Usenet 




Usenet () is a worldwide d ...
.For instance, Chessmetrics articles on  Comparison of top chess players throughout history at  Chessbase
Part 1Part 2Part 3Part 4
/ref>

Chess author  John L. Watson has also referred to Chessmetrics numbers.

 See also

*  Chess rating systems

 Notes



 External links


Chessmetrics site

{{Sports rating systems

 Chess rating systems