The first United States Golf Association Rating system was established in 1911. The proposal made by Leighton Calkins, who served on the USGA Executive Committee in 1907 and 1908) was that par ratings be based on the play of the U.S. Amateur Champion; at the time the amateur champion was Jerome Travers, who won four amateur titles from 1907 - 1913.
Rating courses according to the "expected" score of the national amateur champion became accepted, and course rating was born in America.
Today there is much more of a mathematical component to course rating and its close relative, slope rating, which was developed by Dean Knuth who was dubbed the "Pope of Slope". Knuth, who oversaw a large portion of the USGA staff during his time on various committees, received a degree in mathematics from the Naval Academy and Masters in Computer Systems Technology from the same institution, giving you a reasonable idea of how much brain power went into producing this intricate system.
Course Rating is a measure of the difficulty of courses for a scratch golfer. A scratch golfer, in this use, is defined by the USGA as a male golfer who hits his drive 250 yards and can reach a 470-yard hole in two shots; or a female golfer who hits her drives 210 yards and can reach a 400-yard hole in two (and of course, plays to scratch).
Such a player would be expected to shoot 67 on a course rated near 67, or 75 on a course near 75.
The rating is expressed in strokes and decimal fractions of a stroke, and is based on yardage and other obstacles to the extent that they affect the scoring ability of a scratch player. Course Rating used to be based solely on length. The longer the course, the higher the rating. But obstacles, in addition to distance, are now part of the consideration.
Ten obstacle factors are considered, each of them graded on a scale of 0 to 10, on each hole. Those factors are: Topography, Fairway, Recoverability and Rough, Out-of-Bounds, Water Hazards, Trees, Bunkers, Green Target, Green Surface and Psychological.
Course rating and slope rating are calculated for a course on the basis of a visit to the course by a USGA rating team that involves spending time with the course's staff, spending time on-course taking measurements and typically playing the course before the visit comes to an end.
Based on length and obstacles, and experience gleaned from playing the course, the rating team will evaluate the overall difficulty of the course under normal playing conditions and issue the course rating for scratch golfers.
Along with a Course Rating, the USGA team will also issue a "bogey rating," something many golfers don't realize exists for each golf course. Similar to a Course Rating, a bogey rating is just an evaluation of how many strokes a bogey golfer will take to play the course rather than an evaluation of strokes needed for scratch golfers. And the bogey rating has an important role; it is used in the calculation that produces the slope rating.
Slope Rating (a term trademarked by the USGA) is a measurement of the difficulty of a course for bogey golfers relative to the course rating. The calculation that determines slope is this: bogey course rating minus USGA course rating x 5.381 for men or 4.24 for women.
Slope Rating takes into account the fact that increased difficulty affects such players more than it affects scratch golfers. The lowest USGA Slope Rating is 55. The highest is 155. The "standard" Slope Rating is 113. The Slope Rating is a factor in the calculation of handicap index and is also used to determine the course handicap. For a better idea of how to determine handicap index and course handicap, click here .
Slope itself is a universal standard that enables a golfer to adjust his/her handicap to fit the difficulty of the course he is playing on a given day - i.e., at Pine Valley you'll get more strokes and at the local municipal course you won't get as many; unless your local muny happens to be Torrey Pines South. Obviously, to implement the system, it's necessary to rate every course in the country.
The Kingsmill River Course at Kingsmill Resort was the first golf course in the world to be slope rated under the USGA Handicap System, now in effect throughout the world.
The most important factor of slope is alleviating the inequity for players of different skill levels. For example, let's say Player A and Player B average a score of 85 for 18 holes. But Player A's average is established on a very difficult course, let's say the PGA West Stadium Course (slope of 150), while Player B's average is established on a drastically simpler course with a slope rating of 100. If a handicap was simply an estimate of a players' average score, then these two players would have the same handicap index despite being at different skill levels.
Slope Rating allows the handicap index to reflect these factors. Because he plays on a course with a higher slope rating, Player A's handicap index will be lower than Player B's (when it is calculated using the slope ratings), despite the fact that they both average scores of 85. So when A and B get together to play, B will get those extra strokes he needs.
So in summary, Course Rating is a measure of the difficulty of courses for a scratch golfer and Slope Rating is a measure of the relative difficulty of courses for golfers who aren't scratch players.
Rating America's Most Difficult Courses
Pete Dye's Ocean Course at Kiawah Island is rated as America's most difficult golf course by Golf Digest. The Ocean Course Measures 7,356 yards and has the highest combination of Slope Rating (155) and Course Rating (79.6) in America, according to the USGA.
Located in Bolton, Mass., the International (Pines) Course is a behmenoth playing to an unusual par-73. You'll need that extra stroke, or ten for that matter, considering this course measures 8,325 yards from the tips. The course has a rating of 80 and a slope of 154 from the Tiger Tees.
KooLau Golf Club on Oahu is the king of the forced carry and used to have a slope rating of 162, even though the maximum possible is 155. Currently the course has a slope rating of 152.