Hope this article clears things up. As an Association guy, I can tell you that this issue promote more confusion than just about anything else. The sooner you stop relating slope to difficulty and the sooner slope is not compared course to course, the easier this will be to understand. As the article explains, course rating can be compared, slope ratings not.
Slope: The Bridge Between Scratch And Bogey Golf
by Jim Cowan, Director of Course Rating and Handicapping for the Northern California Golf Association. (From NCGA Golf Magazine)
Here's a simple question: Which golf course is more difficult?
Course A: 72.8/114
Course B: 67.8/127
Easy... at almost every handicap level, the answer is Course A!
Surprised? Many, if not most, golfers probably would have guessed Course B. This just illustrates the many myths and misunderstandings that still abound regarding the subject of Slope.
Myth No. 1: Slope is the primary indicator of difficulty or, to put it another way, the higher the Slope, the more difficult the course.
Wrong! As the above example confirms, it is the Course Rating and not the Slope which is the dominant factor in defining course difficulty.
Since each score a golfer posts is broken down into a numerical value known as a "differential," it is the Course Rating that plays the more important role in the calculation (Adjusted Score minus Course Rating). Slope merely bumps the number from the Course Rating up or down to arrive at a differential.
To put the Course Rating vs. Slope debate into perspective, it takes more than 20 units of Slope to have the same impact as a single stroke of Course Rating for a 5- handicapper. As a golfer's handicap level increases, this ratio of the importance of the two values changes, but even for a 20- handicapper it takes five to six units of Slope to have the same impact as one stroke in the Course Rating.
Myth No. 1a: Two courses with the same Slope are of equal difficulty.
Wrong! A course with a rating of 71.5/125 is about two strokes more difficult than a course with a rating of 69.6/125 at every handicap level.
Myth No. 2: Slope ratings can be compared among courses.
Wrong! I wish I had a dollar for every letter, e-mail or phone call I have received criticizing existing ratings on the basis of the Slope only. In short, there is nothing more dangerous than trying to draw any sort of meaningful conclusions by comparing Slope Ratings from one course to another.
So what is Slope? Slope merely tells you how "proportionately" more difficult that particular set of tees plays for the higher handicapped golfers. The more difficult the tees play proportionately for the higher handicappers, the greater the Slope rating that will be issued.
That's it! Slope doesn't tell you how the course proportionately plays from any other set of tees, let alone tell you how it compares with other courses.
This proportionate difficulty is measured via a Course Rating process that evaluates each hole and each shot through the eyes of a scratch golfer and bogey golfer. This process is so thorough that an actual rating for the bogey golfer is computed, and it is the gap between the Scratch and Bogey rating that determines the Slope.
For example, a set of tees may be issued a Course or Scratch rating of 70.5 and a Bogey rating of 94.3. What this means is that if a scratch golfer were to complete 20 rounds from this set of tees, we expect his 10 best scores to average around 70.5. If a golfer with a Handicap Index of 20.0 were to complete 20 rounds, we would expect his 10 best scores to average around 94.3. Based upon this gap of 23.8 strokes between the two ratings (94.3 - 70.5=23.
, a Men's Slope Rating of 128 would be issued (gap times 5.381 for men).
The Scratch and Bogey ratings are somewhat volatile, and when a series of factors or obstacles on a course tend to gang up on only one of the two golfers, curious things can happen to the Slope.
For example, if a set of tees has a high number of holes in which the bogey golfer can reach the green in "regulation," an upward pressure on the Slope will be exerted. Think about it -- on most of these holes the bogey golfer is approaching the green with a long iron or fairway wood, while the scratch golfer has a wedge or less in his/her hands. Clearly the bogey golfer is much more susceptible to any of the greenside trouble present on the holes which can cause scores to soar (bunkers, difficult chips, etc.). Such a scenario will force the bogey rating higher, widen the gap between the two ratings and result in a higher Slope.
Now consider a set of tees, even on the same course, where most of the holes are unreachable in regulation for the bogey golfer. Now it is the scratch golfer who has the longer approach shots, perhaps with mid to long irons, while the bogey golfer may merely be chipping/pitching to the green in one over regulation. To a certain degree, the tide of proportionate difficulty has turned. Though both ratings will be increased because of the added length of these tees, the gap between the Scratch and Bogey rating may stay relatively constant or may widen at a very slow rate.
These upward and downward pressures help explain why a Slope rating may increase sharply at a course from the Gold tees to the White tees (Bogey rating rising much faster than Scratch rating as the approach shots become longer), yet hardly change from White to Blue (gap increasing slowly due to shorter approach shots of the bogey golfer). It also explains how a shorter course can be issued a Slope rating that may "feel" a little high, or how a longer course may be issued a Slope rating that may "feel" a little low.
Another factor that can greatly impact the Slope is forced lay-ups. If the Scratch golfer is forced to lay up on a hole because of any one of a number of obstacles (water hazard, severe dogleg, etc.), this will increase the Scratch rating. That's because of the extra yardage of the approach shot. It will leave the Bogey rating untouched. This higher Scratch rating narrows the gap with the Bogey rating and decreases the Slope. Conversely, if the forced lay-ups only affect the higher handicapper, the Bogey rating and Slope will increase.
Never were some of these quirks of the system more evident than in early 1999 when 9-hole Course and Slope ratings were issued and 9-hole score posting became an option. I can almost hear the phone ringing now as golfers dispute the Front Nine vs. Back Nine Slope ratings.
Save your phone calls! As you can see, there is much, much more that goes into the development of a Slope than meets the eye, and besides, the Slope rating may not be nearly as important as you thought it was.