11 May 2010

Intermediate Scores as a Match Predictor

For this post I had planned to highlight a remark by GM Alexandra Kosteniuk for Anand - Topalov 2010, Game 8, (Chessdom.com). Commenting on 25...Kc6, she wrote,

Black is in a very difficult position. To tell you the truth, although the match of such players are always awaiting with big interest and enthusiasm, the strategy for this kind of matches nowadays are rather uninteresting. Players, like Anand or Topalov, or even Kramnik are trying to minimize their risk and play positions with a small plus for White and try to hold a draw in boring and slightly worse endgames.

A match is not a tournament, even if you win with the score +1 it's enough to get the title. This makes players play differently, not in an open and exciting style they usually play in tournament, but rather in very academical and unrisky ways.

Then I discovered that I had been pre-empted by The Streatham & Brixton Chess Blog in How long is a piece of string?, where Tom Chivers asked, 'How long should a World Championship match be?' It's a question which has been much debated among chess fans in recent years as matches have been progressively shortened.

GM Kosteniuk's remark raises a number of issues, one of which is Chivers' question. While thinking about it, I started to wonder about the longer, 24 game World Championship matches of the past. How good a predictor of the final result was the intermediate score at game 12, 14, and 16 in those matches?

I gathered the data for 16 matches from my World Championship site (see the sidebar for a link) and loaded it into a database table. After a little manipulation, the following picture emerged.

For each match, it shows the intermediate result after games 12, 14, and 16, together with the final result. For example, the first two lines show that in the 1951 match, Botvinnik led Bronstein by a full point after games 12, 14, and 16 (games 13 through 16 were all drawn), while the match ended in a draw.

It's curious that in none of the 16 matches was the eventual winner behind at any one of the three intermediate stages. The closest match was the 1969 Spassky - Petrosian match, which was equal at all three points (once again, games 13 through 16 were all drawn).

One point worth keeping in mind is that, for all of these matches (except perhaps 1993 Karpov - Timman?), the reigning champion retained the title in case of a drawn match. That meant that he was effectively ahead by one game whenever the intermediate result was tied. The ongoing Anand - Topalov match (the 12th and last regular game will be played starting within one hour) will use tiebreak games in case of a draw.

No comments: