Next look at the 72.0/113 course in blue. The second matters because it's easier to overcome a deficit of 0.2 or 0.3 than a deficit of 2.4 or 3.1. The first matters because the slope has more time to keep adding "tenths of a shot" to the course handicap. The course ratings are quite close together. The difference in handicap indexes is LARGE. The slope tends to matter in only two situations: So, the course rating is the primary determinant of a course's difficulty. But this is because the course rating varies by 3 and 5 (69 to 72 and 74), while the slope can only make up fractions of a stroke (140/113 =~ 1.24 course handicap strokes per 1.0 strokes handicap index). Look at all of the lines, in fact: the yellow line (69.0/140) remains lower for most of the graph than even the two 72.0 courses (blue 113, green 136), and well below the grey course (74.0/118). It's not until you get out to about a 14.0 index that you start to see the expected scores for the 72.0/136 course take over due to the slope. Despite a difference of 18 in their slope, for the majority of these golfers, the 74.0/118 course plays "more difficult" due to the higher starting point of 74.0. Look at the 74.0/118 course (grey) and the 72.0/136 course (green). What these graphs show you is that course "difficulty" is a function of both the "m" and the "b" - the course rating AND the slope. Showing the trend lines much more heavily: The graph of the course handicaps (note that rounding creates some "bumps" in the lines when the slope is not the whole number 1 (113/113): Here's a chart of four fictitious golf courses: Imagine a course with a rating of "100.0" and a slope of "102." Nobody in their right minds would say that course is "easier" than a 72.0/144-rated course. And this leads into what seems to be the biggest misconception. Too many people look at one number - the slope - and use that to determine what the "difficulty" of the course is.īut that fails, because lines are defined by more than their slope: the y-intercept matters. We could keep the same slope and make the course rating 69.0, and the course would instantly be three shots easier for every golfer. These golfers should shoot, on average for the eight rounds that count toward their handicap index, these scores: This should make sense: on a 72.0 (par 72) course with a slope of 113, we have a basic line with a slope of 1. This is a set of tees with a rating of 72.0 (note that I consider all tees to be par 72 for the simplicity's sake in this article) and a slope of 113. In this case, y is the course handicap, m is the slope (slope rating/113), x is the handicap index, and b is the course rating. This line has a "slope" that tells us the "slope rating" of that set of tees. We plot those two points on a graph, and draw a line connecting them. Some basic linear algebra and geometry are used as such: So, we have two numbers: the score for a scratch golfer and the score for a bogey golfer. The bogey rating is the same for a "bogey golfer," (who, oddly, isn't an 18.0 index, but closer to a 20.0, as they're about a 20 course handicap on a 113-slope course). The scratch rating is defined as the score a scratch golfer should shoot on rounds where he plays to his handicap index (of 0.0). Two numbers come out of this calculation: a scratch rating and a bogey rating. A few are subjective, like "how difficult is it to escape if you hit your ball into those trees"? Most of these numbers are pretty objective: the width of the fairway, the length of the hole, elevation changes, the diameter of the green, the depth and size of green side bunkers, etc. This article will assume that you're semi-familiar with the the concepts of course rating and slope, and really seeks to expel some basic myths and misconceptions.Ĭourse Ratings Are the Primary Determinant of "Difficulty"Īs you should know, when a golf course is rated (for "difficulty"), many, many, many numbers are generated for each hole. I've been meaning to write this for awhile, and since the World Handicap System (WHS) is coming to most of the world this year, now's as good a time as any.
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