Chessmetrics
Encyclopedia
Chessmetrics is a system for rating chess
players devised by Jeff Sonas
. It is intended as an improvement over the Elo rating system
.
The weighting of previous matches digresses linearly from 100% for just-finished matches to zero for matches conducted more than two years ago.
Weighting of past tournaments (age in months):
Jeff Sonas, Chessmetrics' author, repeatedly emphasises the importance of a rating system's ability to "predict" results (during testing the results to be "predicted" are those of past games whose outcomes are known to the tester).
Sonas also claims that Chessmetrics has other advantages over Elo ratings:
was inactive for much of 1912–1914, and as a consequence dropped from #1 to #12 in the world in the Chessmetrics rankings, just before his famous victory ahead of all the world's other leading players at the 1914 Saint Petersburg chess tournament.
Chessmetrics can only be used to compare the level of a player against their peers; it is not appropriate to use Chessmetrics to compare players of different era. For example, GM John Nunn has highlighted the absurdity of attempts to compare the objective playing strengths of players from different eras: He used the example of Hugo Suechting
, world ranked 27 and rated 2559 by Chessmetrics in 1911, after the Elite tournament in Karlsbad. An analysis of Suechting's games from that period suggests that his level of play was at best 2100 by today's standard.
Chessmetrics, like any other ratings system, can only be used as a guide.
in October 2002. Since then, Chessmetrics has become reasonably well known, due to numerous articles in Chessbase
and The Week in Chess
.
Respected chess author John L. Watson
has referred to Chessmetrics numbers, and Chessmetrics has been cited in at least two academic papers.
Chess
Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...
players devised by Jeff Sonas
Jeff Sonas
Jeff Sonas is known as a statistical chess analyst who invented the Chessmetrics system for rating chess players, which is intended as an improvement on the Elo rating system. He is the founder and proprietor of the Chessmetrics.com website, which gives Sonas' calculations of the ratings of current...
. It is intended as an improvement over the Elo rating system
Elo rating system
The Elo rating system is a method for calculating the relative skill levels of players in two-player games such as chess. It is named after its creator Arpad Elo, a Hungarian-born American physics professor....
.
Implementation
Chessmetrics is a weighted average 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]
Weighting of past tournaments (age in months):
- 100% * (24 - age)
Perceived advantages
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."Jeff Sonas, Chessmetrics' author, repeatedly emphasises the importance of a rating system's ability to "predict" results (during testing the results to be "predicted" are those of past games whose outcomes are known to the tester).
Sonas also claims that Chessmetrics has other advantages over Elo ratings:
- Elo ratings have a built-in bias against top players, in other words a top player's rating will suffer if he / she achieves against a lower-rated player the percentage result that the players' Elo ratings predict.
- Chessmetrics is more responsive to change than Elo ratings, for example Chessmetrics will track more promptly and accurately improvements in the playing strength of a rising star. Sonas regards this as an important part of Chessmetrics's superior ability to predict results.
- Chessmetrics takes account of the empirically-measured difference in results when playing as White or BlackFirst-move advantage in chessThe first-move advantage in chess is the inherent advantage of the player who makes the first move in chess. Chess players and theorists generally agree that White begins the game with some advantage. Statistics compiled since 1851 support this view, showing that White consistently wins slightly...
, which the Elo system ignores.
Perceived disadvantages
Chessmetrics occasionally gives strange looking results, particularly for players with long periods of inactivity. For instance, World Chess Champion Emanuel LaskerEmanuel Lasker
Emanuel Lasker was a German chess player, mathematician, and philosopher who was World Chess Champion for 27 years...
was inactive for much of 1912–1914, and as a consequence dropped from #1 to #12 in the world in the Chessmetrics rankings, just before his famous victory ahead of all the world's other leading players at the 1914 Saint Petersburg chess tournament.
Chessmetrics can only be used to compare the level of a player against their peers; it is not appropriate to use Chessmetrics to compare players of different era. For example, GM John Nunn has highlighted the absurdity of attempts to compare the objective playing strengths of players from different eras: He used the example of Hugo Suechting
Hugo Süchting
Hugo Süchting was a German chess player.He won at Kiel 1893 took 13th at Leipzig 1894 , shared 2nd with Ignatz von Popiel, behind Robert Henry Barnes, at Eisenach 1896 , and took 15th at Berlin 1897 Hugo Süchting (Suechting) (8 October 1874, Brackrade - 27 December 1916, Valluhn) was a German...
, world ranked 27 and rated 2559 by Chessmetrics in 1911, after the Elite tournament in Karlsbad. An analysis of Suechting's games from that period suggests that his level of play was at best 2100 by today's standard.
Chessmetrics, like any other ratings system, can only be used as a guide.
Popularity
The original article on Chessmetrics was published in ChessbaseChessBase
ChessBase GmbH is a German company that markets chess software, maintains a chess news site, and operates a server for online chess. Set up in 1998, it maintains and sells massive databases, containing most historic games, that permit analysis that had not been possible prior to computing...
in October 2002. Since then, Chessmetrics has become reasonably well known, due to numerous articles in Chessbase
ChessBase
ChessBase GmbH is a German company that markets chess software, maintains a chess news site, and operates a server for online chess. Set up in 1998, it maintains and sells massive databases, containing most historic games, that permit analysis that had not been possible prior to computing...
and The Week in Chess
The Week in Chess
The Week in Chess is one of the first, if not the first, Internet-based chess news services.TWIC has been edited by Mark Crowther since its inception in 1994. It began as a weekly Usenet posting, with "TWIC 1" being posted to Usenet group rec.games.chess on 17 September 1994...
.
Respected chess author John L. Watson
John L. Watson
John Leonard Watson is a chess International Master and author.Watson was born in Milwaukee and grew up in Omaha, Nebraska. He was educated at Brownell-Talbot, Harvard, and the University of California at San Diego, where he took his degree in engineering...
has referred to Chessmetrics numbers, and Chessmetrics has been cited in at least two academic papers.