Update on new GC grading system

The new GC grading system has been in place for just over two weeks.  There are two main changes from the former system.

The first is that a Dynamic Grade ("DG") is an index which always rises after a win and falls after a loss.  The former system used more volatile indices and then calculated the grade as an exponentially smoothed average of a player's most recent indices.  A consequence was that a player's grade could rise after a loss and fall after a win which some found difficult to understand.

The second change is the introduction of Automatic Start Grade Adjustment ("ASGA").  This is a valuable tool which is needed to deal with the large number of new players added to the system every year and the impossibility of knowing in advance how quickly they will improve.  It is not practical for a ranking officer to directly monitor every new player and adjust their start grade if it turns out that they have rapidly reached a much higher standard of play than indicated by their start grade.

ASGA performs this task by comparing a player's Performance Grade for N games with the DG achieved after those N games.  The Performance Grade depends only on the average grade of the opponents met in the N games and the proportion of wins that the player achieved in the N games.  If the Performance Grade and DG differ by more than an amount that varies between 51 and 85, depending on the value of N, the player's start grade is replaced by the Performance Grade for a final run of the calculation program which produces the grades available from the system webpage.

The minimum value of N was originally set at 10 games.  However, since the new system went live on 1 July, it has become apparent that this has generated some very large increases in start grade (300 to 700 points) which lead to equally large increases in DG from performances in events of moderate average playing strength.  These increases are regarded by competent local observers of the relevant players as unrealistic and misleading.  Unrealistically high grades will cause problems with managing grade-based tournament entry and dissatisfaction among peer groups.

The WCF MC has recognised the issue and the force of the criticisms.  It will seek a suitable long-term solution which preserves the use of ASGA but provides a grading system that retains the confidence of all its users.  As an interim measure, the MC has directed that ASGA should not be applied until a player has played 20 ranked games instead of 10.  This takes effect immediately.




New GC grading algorithm implemented

With effect from today, 1 July 2019, the WCF Golf Croquet rankings are based on a new algorithm devised by Louis Nel, a Canadian player and mathematician.  This is similar in effect to the Dynamic Grade used in the Association Croquet grading system.

The block draws for the forthcoming Under 21 Golf Croquet World Championship and Golf Croquet World Championship will be seeded based on grades calculated using the new algorithm.