Here’s more information about course ratings and slope than you probably want.
Once again, the critical point to always remember is this: The course rating on the card says what a scratch golfer (a handicap index of 0) would be expected to shoot. The slope says how much a bogey golfer is affected by the difficulty of the course in comparison to how much a scratch golfer is affected. Higher slope means the bogey golfer is proportionately more affected.
The course rating is created when the rating committee (the Flying L had the course freshly rated after the new gold and red tees were set) walks and plays the course. They look at things like length, hazards and their placement, terrain, green size and break, doglegs, etc., etc. Then they play the course. After all of this they rate each hole for the scores a scratch and a bogey golfer should make from all of the tees. The total of the scratch golfer scores on each hole gives the 18-hole course rating you see on the scorecard. It’s the number that looks like a golf score. The bogey rating is a score like the course rating you see on the card, but the bogey rating doesn’t go on the scorecard. It is used to figure slope.
Just in case you’re curious, here are the Flying L bogey ratings. I calculated them by running the formula backwards, using the slope and scratch course ratings.
Men’s blue – 95.3
Men’s white – 93.6 Womens’ white – 108.5
Mens’ gold – 88.7 Women’s gold – 102.8
Mens’ red – 83.0 Women’s red – 94.0
As a reminder, here are the course ratings and slope for those tees:
Men’s blue – 72.1/125
Men’s white – 70.7/123 Womens’ white – 76.9/134
Mens’ gold – 67.3/115 Women’s gold – 73.1/126
Mens’ red – 63.4/106 Women’s red – 67.1/114
Notice that the difference in the bogey rating and the course rating is greater for tees with higher slope ratings. For example, the difference for the men’s white tees is 22.9 (93.6-70.7) and the difference for the men’s gold tees is 21.4 (88.7-67.3). The difference in a scratch and bogey golfer is 1.5 strokes less from the gold tees than it is from the whites. Or, to say it another way, the increase in difficulty from golds to whites hits the bogey golfer 1.5 strokes harder than it does the scratch golfer.
At the risk of boring the pants off of everyone, consider what that means in practice with this example. (And yes, I know Joe Arredondo really has a plus handicap, not a 0, but I think everyone can identify with him as a good player.) If Arredondo moves from the whites to the golds, he should shoot 3.4 strokes better (70.7-67.3). If a bogey golfer makes that same move, he should shoot 4.9 strokes better (93.6-88.7). The bogey golfer gains 1.5 strokes more than Arredondo when both move from the whites to the golds, the same 1.5 stroke difference that turned up after the calculations in the preceding paragraph. The bogey player gets hammered by Arredondo from either tees, but he loses by a little less on the golds.
It is called slope index because the number refers to the slope of a line on a graph (remember your high school algebra and geometry?) A larger number for slope indicates a steeper line. Larger slopes cause handicaps to go up faster. A well placed pond on every hole might irritate a scratch golfer but it could seriously damage a higher handicap golfer and the degree of damage would increase along with increases in handicap. The presence of the ponds would show up in the slope index.
As a final note of confusion, if you were extra alert you may have noticed that the bogey ratings seem high as compared to the scratch ratings. For example, the difference in the women’s scratch and bogey rating from the Flying L reds is not the 18 you might expect but it’s 26.9. The difference in the men’s gold tees scratch and bogey is 21.4. Both of those sets of tees are close to the standard difficulty slope of 113. The bogey golfer in the handicap system is that “I usually shoot around 90” golfer, not someone with a true handicap index of 18. Because of course ratings and slope of most courses, that 90’s golfer is really more like a handicap index in the low 20’s. A 90 for a man from the gold tees at the Flying L is a 22.3 index. A 90 for a woman from the reds is a 22.6 index.