The World Handicap System defines the difficulty of as:
Hole Difficulty – Scratch Value + Bogey Value – 2 x Par
This equation implies holes are rated for the scratch player and the bogey player. For example, a hole could be rated 4.2 strokes for the scratch player and 5.3 strokes for the bogey player. However, an examination of previous USGA Course Rating Manuals and a description of the USGA Course Rating Model by its creator, Dean Knuth, does not reveal how holes are rated for difficulty. The USGA Course Rating Model does indicate how “courses” are rated, but not “holes.” The USGA’s Course Rating equation is:
Course Rating – Effective Distance/220 + 40.9 + Scratch Obstacle Value (SOV)
Course Rating Committees does not assign a stroke value to the obstacles on each hole. Instead, the process goes as follows:
- These values are weighted in accordance with importance (e.g., for the scratch rating use topography .10, trees .09, etc.)
- The sum of the weighted values and multiplied by .11.
- The SOV is the product found in step 3 minus 4.9.
If this sounds more like a cookbook recipe than an empirically based econometric model, that is because it is. But put that aside. The USGA model will at least give consistent, if not accurate, estimates of the SOV. That is, courses with similar obstacles will get closely the same SOVs. The USGA model as described above will not, however, yield a stroke obstacle value to each hole.
So how are ratings for each hole determined? The question was put to Scott Hovde, Director of Course Rating and Handicap Education, at the USGA. Below are excerpts from the email exchange:
Hovde: A scratch value for a hole would be based on the combination of a (sic) the length rating and the obstacle stroke value. The length rating has not changed in a while (other than name, which used to be yardage rating)...It is probably listed as an 18-hole formula, so would have to be scaled down to a single hole, but a hole over 420 yards for men (effective playing length) would have a length rating of 4.2 or greater. The obstacle stroke value can add or subtract from that, but on average it adds to it.
OnGolfHandicaps: Your example implies there is a formula for converting hole length into the scratch and bogey values mentioned in Appendix E. Can you cite a reference that explains how the course distance rating is scaled down to a single hole?
Hovde has not replied to this request for details on how hole estimates are actually made. Equally disappointing were responses from the Southern California Golf Association (SCGA) and the Oregon Golf Association (OGA). Doug Sullivan, Director of Course Rating at the SCGA, has published hole ratings but has tacitly refused to explain his method for doing so.
Gretchen Yoder, Manager of Handicapping and Course Rating at the OGA, wrote the following:
I guess the best way to think of it is separately for both Scratch and Bogey, the number of the full shots, plus the distance of the shots to the green and then +/- any difficulty in addition to yardage.
Yoder’s description is not definitive of the method. How does a 140-yard distance to the green translate into an incremental hole rating? And how is the +/- difficulty determined?
Why are the USGA and regional golf associations so secretive about the hole-rating process? One explanation for the cover-up is the USGA does not want to expose the lack of scientific rigor in the Course Rating process. The USGA, for example, has never published any research indicating its hole ratings predict scores with any accuracy. The USGA thrives on a on a reputation of omnipotence (Chambers Bay aside). To be forthcoming about much of its work on the handicap system is not in its own best interest.
 Rules of Handicapping, Appendix E, United State Golf Association, p. 98.
 USGA Course Rating Manuals, 21012-2015, 2016-2017.
 Knuth, Dean, “A two parameter golf course rating system,” Science and Golf, E & F Spon, London, 1990, pp. 141-146.