Stroke Handicap Index

Stroke Play Handicap Index

Background

Golf is played in two fundamentally different formats: Match Play and Stroke Play (Stableford and Par are varieties of Stroke Play).  Both formats are commonly played in Handicap form, at least at amateur level.  The Handicap Index for Match Play and Stroke Play is usually quite different to accommodate the differences in the two formats.

Golf Australia has developed a generic Match Play Index which gives “a fairly even distribution throughout the round”.  The Grange golf club uses that index and it is not discussed here.

For Stroke Play the Handicap Index needs to reflect accurately the difficulty of the holes on the course in order to allocate handicap strokes where players need and should be receiving them.  Common practice in determining the Stroke Play Index has been to rank the hole difficulty by either looking at the hole-by-hole scores returned by low handicap players (A grade) or, less commonly, the scores returned by all players, and then distribute the Handicap Strokes accordingly.  The problem with this approach is that low and high handicap golfers have different abilities and skills and play the game quite differently.  For example, high markers usually find Par 5 holes demanding as they need to play three good shots in a row to be near the green and this becomes less likely as the handicap increases.  On the other hand, low markers will regard Par 5s as birdie chances as they hit longer and more accurate shots.  Similarly, low and high markers may have different views on which hole on the course is the hardest but this really only matters to the low handicap player as this is where they need a stroke and the high marker will get a stroke on many holes including the hardest.  A concern with using A grade scores to determine the Stroke Play Index is that a small population of players is determining the handicap index.  This can be seen in Tables 1 and 2 and the associated graphs which show the number of rounds played in various handicap ranges for The Grange West Course Blue and Red tees over a two year period.  For the Blue tees A grade players contribute only 28% of rounds and for the Red tees only 25% of rounds.

Table 1. Number of Rounds as a function of Handicap. West Course BLUE Tees

Table 2. Number of Rounds as a function of Handicap. West Course RED Tees

The considerations above suggest a different approach to determining the Stroke Play Index may be appropriate.  Golf Australia suggests the use of a more comprehensive statistical method with more granular data analysis.  This method is outlined below and used to determine a new Stroke Play Index for The Grange’s courses.

Stroke Play Index Determination Method

Golf Australia has recommended a method which is more likely to allocate handicap strokes at the holes where they are needed by players of various handicap.  The procedure is as follows:

1. Players are split into handicap groups and the average over par score is calculated for each hole for each group. The handicap range used for the groups is six giving groups of 1-6, 7-12, 13-18, 19-24, … etc.
2. Within each handicap group the holes are then ranked according to the average over par score to give the hole difficulty ranking for each group.
3. Determine the 6 most difficult holes (i.e. the 6 hardest holes for the 1-6 handicap group) and assign them handicap indices 1-6.
4. Determine the 6 most difficult holes, which have not already been assigned an index, for the 7-12 handicap group and assign them handicap indices 7-12.
5. Repeat this process (Step 4) across the remaining handicap groups.

The use of this method leads naturally to the use of Split Indices because it is unlikely that, when allocating strokes to groups with handicap 19 and above, the same hole index order would repeat (i.e. 1/19, 2/20, 3/21, …, 18/36).  This is because high and low markers will often find different holes more difficult.

The Data

Data were downloaded from MiClub for the two year period June 4, 2014 through June 4, 2016 for the West Course and East Course, Blue and Red tees. Table 3 summarizes the number of rounds/cards.  Note that there were fewer rounds for the East Course than the West as only rounds completed on the East Course after its slope index was re-rated were considered.

Table 3. Number of Rounds for each Course and Tee

The Results – New Stroke Play Indices

The Grange currently uses Stroke Play Indices which force indices to be even on the front nine of the West Course and odd on the front nine of the East Course.  It has been decided to generate the new indices so that the Even indices are on the Front nine of both courses.  Charts showing the hole difficulty ranking as a function of handicap for The Grange West and East courses and the resulting handicap index assignment, with the constraint of Even indices on the Front nine, are shown in Appendix 1. 

The Golf Australia method for determining the Stroke Play Index leads to the following new course indices:

A number of observations can be made:

1. West Course BLUE tees:
   1. The second stroke on Par 3s is given for handicaps 33-36
   2. Hole 17 becomes the number one hole.
   3. Holes 11 and 17 have previously been indexed considerably too high whereas Hole 15 has been indexed too generously.
2. West Course RED tees:
   1. Holes 7 and 11 play very much harder than they are currently indexed whereas Holes 9, 12 and 13 appear to be easier than they are currently indexed.
   2. The second stroke on Par 3s is given for handicaps 32 and above.
3. East Course BLUE tees:
   36. Except for Hole 5, second handicap strokes on Par 3s are given for handicaps 34-36.
   37. The current index for Hole 4 is significantly too high.
   38. Hole 8 is currently indexed too generously.
4. East Course RED tees:
   1. Hole 2 appears currently to be too generously indexed.
   2. The second stroke on Par 3s is given for handicaps 32 and above.
   3. The current index for Hole 4 is significantly too high.

In Conclusion

This method for generating Stroke Play Handicap Indices has the advantage of allocating handicap strokes on the holes where they are needed based on the playing characteristics of golfers at various handicap levels.  It leads naturally to the introduction of Split Indices given that playing handicaps can be greater than nineteen.  Many clubs use Split Indices and club golfers are familiar with this concept.  Furthermore, at The Grange, the number of handicap strokes given at each hole is printed on the score card so the use of Split Indices would not be of concern to players.

The new indices have been developed using playing data for the Blue and Red tees and it is expected that the indices would apply to those tees.  Consideration should be given to determining new indices for the White tees using the same procedure.  Likewise, new indices may be considered for combination courses, such as the President’s and Captain’s course, and also for individual nines of each course.
Appendix 1.   Hole Difficulty Rankings for The Grange West and East Courses as a Function of Playing Handicap.

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