Welcome to Ratings Central, home of the world’s most accurate rating system!
On June 1, 2019, we will be modifying the temporal-update algorithm and will reprocess all events. Everyone’s rating will change. All historical ratings will change.
Currently, if the rating system has not seen a player for a year, the standard deviation of the player’s law will increase by at most 70 points.
With the new algorithm, if the rating system has not seen a player for a year, the standard deviation of the player’s law will increase by at most 79.4 points and the mean will increase by 7 points. However, the increase in mean will not be credited until the player plays in an event. (The new temporal-update is the sum of a mean-zero normal random walk with a variance of 70² per year and a Poisson jump process with jumps of 200 points, a mean of 7 points per year, and a variance of 200 × 7 per year.)
When we reprocess all events, the ratings of 99.99% of the players will increase or stay the same. The average gain will be 42 points. Only 0.02% of players will gain more than 300 points.
We were motivated to consider changes to the algorithm by a major event director who felt that the ratings for their players were deflating. After a year of experimentation and investigation, we concluded that part of the deflation was due to their choice of priors. However, even after using better priors, there still appeared to be some deflation. A related problem is that sometimes the system can be slow to react when a player improves rapidly. We think the new temporal-update algorithm produces more accurate ratings.
TT = Table Tennis. HTT = Hardbat Table Tennis. STT = Sandpaper Table Tennis.