The USGA estimates Course Ratings to the nearest tenth and Slope Ratings to the nearest point. As pointed out in a previous post (How Accurate is the Slope System?, 10/8/2012), there is larger uncertainty in the Ratings estimates than the USGA cares to admit. A course that has recently been rerated by the Southern California Golf Association (see Appendix) demonstrates the spurious accuracy of ratings. This note is not written to complain about the Ratings, but to illustrate the problems of making accurate ratings. Ratings are not a science and only an art in the same sense that finger painting is an art form. This can be demonstrated by examining the new and old ratings at the rerated course.
Course SetUp – A major rating problem occurred when the course was shortened for men (green tees). The green tees, according to the scorecard, are a combination of white and red tee placements. (Note: There are no green tee markers.) The actual placement of the green tees, however, is different. On 15 of the holes where the green tees and red tees should be of the same length, the green tees are typically set at least 10 yards behind the red tees. This is probably done so men can retain the illusion they are not playing from the red tees. Similarly, when white and black tees are supposedly shared, the black tees are placed 1015 yards back from the white tees. Then there are outright errors in tee placement. The green tees are supposed to set alongside the white tees on one hole. Instead, they are set alongside the red tees making for an error of some 60 yards.
So what course did the SCGA rate? Apparently, it rated the course shown on scorecard since that is the distances it reported. In essence, the SCGA has rated a course that does not exist.
Ratings Changes – Sometimes Rating Committees make small changes just to justify their existence. The small changes in the ratings at the course (e.g., one point change in the Slope Rating) are not due to changes in the courses, but changes in the Rating Committee. The Committee does not have to explain the ratings, but only send them along to the Club as if they were inscribed in stone. Could the Committee actually state a physical reason for a Course Rating increasing by 0.1 or the Slope Rating by one point?
Posting 9holes or 18holes –Courses are rated by each 9holes. The 18hole Course Rating is the sum of the two 9hole Course Ratings. The 18Hole Slope Rating is the average of the two 9 hole Slope Ratings rounded to the nearest integer. The rounding error in the 18hole Course Rating could be as much as 0.1. The Slope Rating for 18holes will be the same whether the difference in the 9hole Slope Ratings are some odd number or that odd number plus one. For example, the Course Rating from the Gold Tees is 73.7 and the Bogey Rating is 98.5. The Slope Rating for 18holes should be 133 (5.381∙(98.573.7)). The two 9holes Slope Ratings are 130 and 137. When the Slope Ratings are averaged and rounded, the 18hole Slope Rating is134.
Whether a player posts an 18hole score or two 9hole scores can make a difference. Suppose a player shoots a 90 from the gold tees. His differential is 13.7 ((9073.7)∙113/134). The table below shows that if he posts various combinations of 90 as 9hole scores, his differential can be as high as 14.0 and a as low as 13.6. In essence, player who shoots 4050 is considered a better player than one who shoots 5040.
Table
Combined Differential for 9hole Scores
Front Nine Score
CR =36.5 SR=130

Back Nine Score
CR = 37.2 SR = 137

Combined Differential

50

40

14.0

49

41

14.0

48

42

14.0

47

43

13.9

46

44

13.9

44

45

13.8

44

46

13.8

43

47

13.8

42

48

12.7

41

49

13.6

40

50

13.6

World Handicap System (WHS) – The USGA Course Rating System is based on taking a player’s best 10 out of 20 differentials. The WHS will only use a player’s best 8 differentials in calculating his Index. Therefore, as of January 1, 2020 every Course and Slope Rating will be in error. Rather adjust the Ratings, the USGA will just let the Indexes of every player drop by approximately 0.5.
Lessons Learned – This post continues the blog’s efforts to document the uncertainty surrounding the accuracy of Course and Slope Ratings. Recent changes in the Handicap System only introduce another layer of complexity without an accompanying benefit. The best example is the Daily Course Rating (DCR) to correct for bad weather now part of the World Handicap System (WHS). Below is the equation used by Golf Australia to make that adjustment.
DCR = SR +SUM(36+ParSRCPAmhbS)/(m’h+b’)^{2)}/SUM(1/m’h+b)^{2})+1/CSD^{2})
It is assumed the WHS has a similar equation. Any regulation that is not understood by those being ruled is not a good one. Moreover, the Handicap System is marked by rounding errors, measurement errors (see above), random errors, and systematic errors (i.e., sandbaggers). To believe a quadratic equation can make a significant advance in the equity of competition is myopic. Sadly, such claims are often made by “quants” and adopted by administrators who are dazzled by the mathematics. This fulfills the bureaucrats need to do something even though it is of little or negative value.
The major lesson in all of this is to not take handicap ratings too seriously. They are not precise, but “good enough” and probably as good as can be done. Errors in ratings can cause you to lose and win a match. Things should even out in the end
Appendix
Course and Slope Ratings
Tees

Old
Course Rating

New Course Rating

Old Slope Rating

New Slope Rating

Old Yardage

New Yardage

Gold

73.5

73.7

133

134

6972

6972

Gold/Black

72.2

72.3

129

130

6689

6689

Black

71.0

71.2

126

127

6445

6445

Tournament

70.0

70.0

124

124

6195

6195

White

68.4

68.4

119

120

5851

5870

Green

66.0

65.7

111

112

5365

5204

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