2.3 Jackpot: Who Owns 2000 Points?

Rating is always relative (See section 3.4 How Can I Get a Rating?.). The rating number of a player makes only sense if compared to a rating number of another player. If we move the scale of the ratings collectively, the rating difference does not change. in other words: The offset is arbitrary.

The system was initialized with the ISK ratings as of 1999-01-01. Because is started as a German system, only the ten German ISK-ranked players were considered. These players defined the reference group.

The new scale was shifted until the mean rating of the reference group matched their mean ISK-rankings. This was done to keep the ratings within the same range.

The initial definition of the reference group had some drawbacks:

• Some of the players have retired from tournaments and have no reasonable rating any more.

• The group was too small. If one of the players scored very successfully in a tournament, the mean value of the reference group suddenly changed, causing the ratings of all players to change in the same way.

Therefore the reference group has been redefined. Keep in mind that the concept of the reference group is to define a group of players, which do not change their playing strength over the years. The top players must be excluded, because they do improve their skills by learning from theory and history. The weak players are not a good choice, because they play infrequently and therefore they have no reasonable rating.

Therefore the recipe for creating the reference group is as follows:

• Start with all players.
• Remove the top quarter of the players.
• Remove the lower half of the players

Note: The concept of the reference group helps to keep the ratings comparable over a long time. The ELO-system has no reference group. It assumes (without stating this explicitly), that the mean strength of all players does not change between the tournaments. This is wrong. Even worse: The strength grows significantly! This is, because the tournament beginners are young and have a low playing strength. They retire, when their playing strength is significantly higher. Therefore the ELO-ratings are deflating continuously, causing a lot of discussions in the chess community.