ICCF Ratings

The ICCF Rating system

by Nol van ’t Riet (NED), updated by Gerhard Binder (GER) and Mariusz Wojnar (POL) 

Players in this list for the longest periods are:

These are the names of the players who have been leading in the correspondence chess world in the second half of the 20th and the beginning of 21st centuries. To be in the top five for ten or more years means to you must have devoted almost your whole life to correspondence chess.

Another interesting list is the list of the players with the highest ratings ever:

It’s important to realise that the group of players in the system increased from 167 in 1950 via 8,752 in 1987 to 31,050 in 2002 and up to 39 784 in 2011. This means that in every range of ratings there will be more players with a rating in that specific range. So that’s why also at the verges of the system there will be more players with a high (or a low) rating. So it’s not a matter of inflation, but a matter of spreading of the ratings.

The most important feature of ratings is that they are corrected when a player ends new games. These changes are essentially illustrated in the chart below. For example the final of the 10th World championship has been taken. This tournament has been carried through from 1979 until 1984.

The real procedure is slightly more complicated than outlined below. The simplifications that have been made have the intention of explaining more clearly the thoughts behind the rating calculations. The order of the players is according to the points they scored at the end. These can be found in column 5.

Column 1 gives the ratings of the players at the start of the tournament. Using these ratings one can calculate that the average rating is 2536. This number indicates the strength of the tournament. It also makes it possible to compare this strength with those of other tournaments. The final of the 11th World Championship for instance had a rating of 2520, the final of 12th a rating of 2531, the final of the 15th a rating of 2556. In column 2 you find the difference of each player with average rating. A minus sign indicates the rating of this player is below the average. With the differences from column 2 the most important part of the calculation starts. Differences are looked up in the table below. This table gives the ‘expected score’ in percentages, for everybody.

For Richardson, you find in column 2 a rating difference of + 79 rating points with the average of his opponents in this tournaments. As he is supposed to be stronger than this average opponent he is expected to score over 50%. The above table points out that a rating difference of + 79 rating points belongs to a positive (H: higher) score of 61%. So Richardson was expected to score 61% against his 15 opponents. Column 3 gives this expected percentage score for each player. Column 4 shows the score in game points (rounded upwards) corresponding to that percentage score. So Richardson was expected to score 9½ from 15 games

In column 5 you find the real scores in the tournament. Comparing the columns 4 and 5 shows that Palciauskas not only was expected to win the tournament, but he did with one point more than expected. To him that was rather appropriate, as Morgado and Sanakoev particularly, had played much better as could be expected on account of their start ratings. Columns 4 and 5 also show that Seeliger, Estrin, Sørensen and Kalish achieved a disappointing score.

After the tournament is finished the difference between the expected score (column 4) and the real score (column 5) is used to calculate a new rating for each player. This difference is multiplied by 10 and with that result the old rating is increased or decreased, according to the fact if the player has scored above or under his expectation. Column 6 holds the thus calculated new ratings.

As indicated above, real calculations are somewhat more complicated. We mention the following differences:

• § it is possible that at the beginning of a tournament some players still do not have a rating as they haven’t already finished enough games. The rating rules contain a procedure to give those players temporarily a provisional rating
• § in reality, the expected score of column 4 is calculated as the sum of expected scores in all single games. No rounding offs are carried through
• § sometimes another number is taken instead of the 10 that is used to multiply the score difference with in order to calculate a new rating. This depends on the number of games someone has already played and also on the value of his old rating
• § if a player has scored extremely above (Morgado and Sanakoev) or under (Estrin and Kalish) his expectation extra rating points are added or subtracted. The reason why is that an exceptional result could indicate that the start rating of the player was no longer adequate. Therefore it is important to steer the player quickly towards a proper rating
• § tournaments like the above mentioned World Championship may last many years. Some games are finished very rapidly, others take four or five years. Some players participate in the meantime in other tournaments, some players don’t. In order to rate results of those differences in a proper way, all players get a new rating each year. Therefore it is done as if the player has played in a tournament with just those opponents with which he ended a game in that particular year.

Not all players are equally pleased with their own ratings. During the years of the construction of the ICCF rating system it has very often appeared that lots of players have their own subjective view on their own playing strength and on those of others.

One is often inclined to hang up ones own playing strength on that one best result one has achieved many years ago. The majority of less good results are forgotten. In this respect it is worth remarking that a rating system only counts the full and half points and zeros which a player achieves. Not illness, lack of time, personal problems, blunders, writing errors, sacrifices for the team, nor brilliant insights – and no matter in which tournament the win of player A against player B was achieved: the win is a win, whether the game was played in a World Championship final or in a friendly country match.

For CC players who are used to playing lots of tournaments at the same time, ratings are not so pleasant. For in the ratings are also included the results of the games which were played with less effort. To Palciauskas (see above) this meant that his rating in the list of 01.01.1984 was not 2675, but only 2430, because in the same period in which he won the World Championship he also participated in the final of the 2nd ICCF World Cup with the result of 3 in 16 games against an average rating opposition of 2333.

It was hoped that the adoption of a rating system in ICCF would reduce the phenomenon of players not trying their best in some tournaments, or withdrawing from others.

Ratings – rules improvement adopted by ICCF Congress 2011 in Finland

Information presented below comes mostly from the ICCF Congress minutes.

Rating Commissioner Gerhard Binder (GER) during ICCF Congress 2011 in Järvenpää (Finland) conducted a working group for all those interested delegates prior to his official report as the topic was highly technical and perhaps not everyone wanted to sit through the details. The following was discussed (round of experts and then with delegates):

At previous Congresses, I always had to report strange cases abusing the concept of start ratings. Already in 2010, I checked some variants to avoid such problems and to improve the system. However, I was not able to present a proper solution to the Congress in Kemer. Additional statistical research was necessary to find out what is the best-suited formula for the difference of ratings, which is the base for the evaluation of a game.

Since 2000, we are using the difference in the start ratings of both players, independent from their rating development during the game. This was a logical method to ensure that all games of a tournament were treated equally whenever they were finished. However, with ongoing time the concept was criticized more and more, not only due to the mentioned strange cases. For new players, especially in open tournaments, the start ratings were sometimes too low and damaged the rating of higher rated opponents who often refused therefore to participate in Cups or Jubilee tournaments.

After some simulations and discussing five possible solutions especially with my deputy Mariusz Wojnar, I favoured the idea to use the recent published rating for the player and the higher value of start rating and recent rating for the opponent.

Using newest ratings for the calculation is of course the most accurate method following the theory of Prof. Elo and near to the thinking of the players. It works fine, if a tournament is finished within a short time and is evaluated before the next tournament starts (OTB). In CC we have a totally other situation. The results of a tournament come in over different periods and other tournaments are played simultaneously. This may lead to strange distortion for the players in one tournament, especially if an opponent drops down dramatically due to withdrawals in other events. The current situation is also unjust if the opponent’s start rating does not correspond to his real strength and he goes up during the tournament due to good performance. To use the better value (start rating, recent rating) is a good compromise to reduce such injustice. Of course, such a choice for a higher value has hidden dangers for the balance of the system (inflation).

To estimate this danger and to further convince Mariusz and myself (and with a tremendous amount of time!) I made step by step a complete recalculation of all rating lists from 2000/1 (when the start-rating concept was introduced) to 2011/3 using this proposal. This comprised 28 rating lists with all players who finished at least one game during that period (18 443 players). After removing those players who do not have a published rating in 2011/3 13 492 players remained. Analysing their rating performances convinced me that this way of calculating the rating difference does not produce inflation but, on the contrary, rather compensates the existing deflation.

Presentation of this simulation was given at Congress which of excerption is placed below.

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Charts ilustrating Gerhard’s analysis

Development of average ratings for the period from 2000 to 2011

The following chart shows the avarage of fixed ratings for only those players who were on all ratinglists from 2000 to 2011 (constant player pool)

Using a constant player pool (4191 players) avoids the influence by changing the structure of players and shows the real development of the avarage fixed rating. Here we have a deflation of 46 points in 11 years, a fact which I observed in recent years. This is a weakness which affects categories and title norms. The new strategy would reduce this effect to 18 points in 11 years. This may be acceptable having in mind that all players of the selected pool became 11 years older during the considered period. Further development has to be watched carefully.

The chart shows the numbers of only those players who were active from 2000 to 2011 (grouped by range of 100 ratingpoints)

[Show as slideshow]

Charts above present comparison for a single player (just few examples)

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Gerhard’s analysis above did generate quite a bit of discussion.

Summary

In summary, here were the items discussed and agreed to:

Present Situation

Ratings are calculated on the difference between players ratings set at the beginning of the tournament = start rating. The problem addressed is results of tournaments are spread over many rating periods with rating changes by players occurring.

Present Situation – Advantages

• All games within one tournament are treated equally
• The players know the effect on their ratings of any result at the beginning. It doesn’t matter when the game is finished.

Present Situation – Disadvantages

• New ratings are calculated by an increment to the base (last published rating) which is calculated using base-independent values. This leads to distortion.
• New players may have a too low start rating which damages the ratings of their opponents.
• The system may be abused by playing many games with artificially low start ratings.
• We have a significant deflation of average ratings during last 11 years.

Proposal

The rating difference is calculated by a new formula. For the player, the rating of the valid rating list at the end of the game is used. For the opponent, the higher value of his last rating and his start rating is used.

Proposal – Advantages

• The mix between base value and calculating the increment will be avoided.
• If an opponent’s rating goes up during the running time of a game, the player gets a more accurate probability; if an opponent’s rating goes dramatically down (normally due to other tournaments), his or her original strength is considered.

Proposal – Disadvantages

• Games in one tournament are treated different; the outcome depends on the time when a game is finished.
• Proposal – Considerations
• Possible delay in resigning or accepting draw by players who are staring at their ratings (called DMD).
• Possible inflation of average ratings by including a choice for a higher value.

Proposed Change to Tournament Rule 7.4

When a game is finished, the rating calculation procedure will use a player’s rating from the newest rating list for those players with a published rating; otherwise, the start rating is used. However, if a player’s current rating is lower than his start rating; the new ratings for his opponents are calculated using the player’s start rating.

Proposed Change to Rating Rules

The expected game result (We) is the percentage expectancy, obtained from item 4, based on the difference between the player’s rating and the opponent’s rating as defined in Tournament rule 7.4 (Rule number will be revised – this may change). If this difference is greater than 350, it is set to 350 for the evaluation.

A player without a published ICCF rating at the start of the tournament and without an applicable FIDE rating will be regarded as having a start rating equal to the tournament level (see item R 11 – Assumed start rating for a player without a published rating at the beginning of a tournament).

An additional change to Rule 7.7:

Players who do not qualify for a new rating because they have not finished a game during the evaluation period, remain on the active list because

• (a) they have finished a ratable game during the recent two calendar years, or
• (b) they are participating in at least one running tournament (rated or unrated).

Other players retain their most recent published rating, but are no longer shown in the published list. However, the webserver shows all players with their valid rating.

A proposal addendum was added by the Deputy Rating Commissioner, Mariusz Wojnar (POL) who recommended that the rating rules become part of the Tournament Rules (as an appendix). Also, he suggested that the Norms and Categories chart (always difficult to find) also be included in the Appendix to the Tournament Rules.

Implementation

ICCF Congress 2011 accepted above mentioned proposals, including the new rating calculations and modifications to the rating rules effective with the first rating period of 2012 (it means for games finished from 01.09.2011). The calculation programs were changed on the ICCF webserver in September 2011. Prediction option is following new rules, as well.