THE RULES CORNER
Articles about everyday rules we encounter, not the strange,
odd ball situations that make it to the news
Ask most players what their handicap is based on, and they will reply, "It is based on my best 10 scores out of my most recent 20 scores". Well, sorta. A score of 85 on an easy course like Los Lagos isn't the same as an 85 at Santa Teresa, and especially at Pasatiempo shooting 85 is much harder.
For that reason, Ghin records both the Score you post and the corresponding Differential. The differential (Diff.) is made up of not only your score, but also the rating, slope, and the tees on the course you played. That information comes up automatically on your home course (or courses) when you post a score, but you must put it in on other courses or if you are posting an 'away' score at your home club.
USGA uses the differentials to figure your monthly Index. This index is 96% of the average of your ten lowest differentials, and appears on your PWGA Revision Update each month. (This is the general rule, but may be modified by Tournament Scores, etc.)
You will see all the data for your last 20 games as the last screen anytime you post a score, so take a minute and look at it before you hit the final 'Return'. You also can see it on your computer by logging into your eClubhouse account.
Below are some examples of rating/slope affect score at different courses. Comparison at Santa Teresa is for our old White Tees, because the slope/rating for the Blue Tees and new White Tees may change.
The formula for a Diff. is fairly simple, but contains a Constant of 113 which (I believe) is considered an 'average course'.
Diff. = (Score – Rating) *113/Slope - Example: 100 on Santa Teresa, rating 74.4, slope 126:
Diff. = 100-74.4 [=25.6] *113 [=2892.8] divided by 126 [=22.96, round up] so your Diff. is 23
[numbers in brackets like these show the result of the previous calculation]
If you play some other courses the way you played a 100 at Santa Teresa, here is what you would score:
Just for fun, here are those same courses showing what the differential for scores of 85, 95, and 105.
Course Rating Slope Score Diff. Score Diff. Score
Los Lagos – red 65.1 108 85 20.8 - 95 31.3 105 41.8
Santa Clara 71.1 114 85 13.8 - 95 23.7 105 33.6
Santa Teresa 74.4 126 85 9.5 - 95 18.5 105 27.4
Shoreline 70.4 120 85 13.5 - 95 22.9 105 32.3
Coyote Tournament 70.0 128 85 13.3 - 95 22.4 105 31.5
However, be aware that I used some old cards to get the Rating & Slopes of these courses so it is possible that they have changed. Check a new card to see if the information above is still correct. If not, figure the new and correct Differential using the formula above. Also – remember the data on the Pro Shop Card may not be the same as the one the Women's Club uses. Ghin rates a player according to the information given by the Handicap Chair of each group.