K-Factor Change - May 2013 Print E-mail
May 13, 2013

The US Chess Executive Board has approved two changes to the US Chess Ratings System! They will go into effect with tournaments ending Saturday 18 May 2013.

First, the Effective Games portion of the ratings formula is being changed to lower the number of effective games for players rated under 2355. This change will cause many ratings to go up and/or down much more quickly by changing the K-factor. K-factors, which determine the pace at which ratings change, will be increased for many rating levels. The higher the K-factor, the more volatile the rating. The amount that the K-factors will be increased is especially large [about a 40% increase] for players rated between 1900 through 2100. However, these ratings will still change more slowly than they did for many years prior to 2001 when the K-factor for ratings of 2100 and below was 32. Most other rating levels will see smaller K-factor increases. The new K-factors apply to Quick and Blitz ratings as well as Regular Ratings.

Second, the K-factor for higher rated players in fast time control events [dual rated] will be lowered. This is intended to cause Master Regular Ratings to change more slowly from Dual-Rated play. The intention, here, is to cause the ratings of our top players to better reflect play at classical time controls, and to decrease the chances of players qualifying for invitations based on play at G/30 to G/65 who may be stronger at these time controls than at slower ones.

More resources on the Ratings System and the announced K-Factor Change: