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10 Index Differentials by Rating/Slope


iacas

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I thought some of you might find this chart interesting. I've been aware of this for awhile, but it's good to see it in yet another form. This chart is from Arccos, and illustrates what many of you have felt to be true for awhile.

This is the average differential for 10 handicap golfers at these ratings and slopes.

image.jpeg

Now, for those of you saying that they should all be around 10, just remember: their 10 index comes from their best 8 of their last 20 scores, not the average of all differentials.

For those of you saying that they should all be about the same, they're closer than you think: 10.7 to 13.2 is only 2.5 shots, and that's at the REALLY extreme edges of 75+/140+ and 66/112 or so. That's a pretty big difference. Most of a course rating is distance… so perhaps it doesn't scale quite at the rate it should.

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Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
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  • iacas changed the title to 10 Index Differentials by Rating/Slope
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I’m surprised by that chart - if I’m interpreting that correctly, they scored better on the more difficult courses.  I guess that’s because the extra strokes don’t penalize them as much in the tougher courses?

Driver: :callaway: Rogue ST  /  Woods: :tmade: Stealth 5W / Hybrid: :tmade: Stealth 25* / Irons: :ping: i500’s /  Wedges: :edel: 54*, 58*; Putter: :scotty_cameron: Futura 5  Ball: image.png Vero X1

 

 -Jonny

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8 minutes ago, woodzie264 said:

I’m surprised by that chart - if I’m interpreting that correctly, they scored better on the more difficult courses.

No, they didn't score better. They got slightly better differentials.

  • 66/112 @ 13.2 = 79.3
  • 75/142 @ 10.7 = 83.5
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Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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In my experience, the higher slope/course rating courses the tees are frequently up from where they "should" be. I'm guessing very few people adjust their course and slope ratings for tees not being all the way back. For example, at Bethpage Black, the blue tees are 77.5/155. They are based on a yardage of I think 7,468. I have never seen the blue tees all the way back on seven of the holes in perhaps 40 playings. My guess is some of this at least is driven by where the tees are. 

The other driver here would be where players' strengths lie. I tend to wind up with better differentials on higher slope/course ratings, just because pars on hard holes I find easier than birdies on easy holes. 

I'd also be curious how much data there is in the tails here. I think I've seen one course with a slope below 113. That's the pitch and putt course at Flushing. That is par 54. Course rating was something like 50.8 and slope was 78. It's in awful condition and it'll take you five hours to play a round. 80% of the people playing have never played before. I played half decently and shot 59, which was about a 12 differential. I'm not sure even a PGA tour player could pull off a scratch handicap playing purely that course.

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On 11/16/2023 at 7:56 PM, iacas said:

I thought some of you might find this chart interesting. I've been aware of this for awhile, but it's good to see it in yet another form. This chart is from Arccos, and illustrates what many of you have felt to be true for awhile.

This is the average differential for 10 handicap golfers at these ratings and slopes.

image.jpeg

Now, for those of you saying that they should all be around 10, just remember: their 10 index comes from their best 8 of their last 20 scores, not the average of all differentials.

For those of you saying that they should all be about the same, they're closer than you think: 10.7 to 13.2 is only 2.5 shots, and that's at the REALLY extreme edges of 75+/140+ and 66/112 or so. That's a pretty big difference. Most of a course rating is distance… so perhaps it doesn't scale quite at the rate it should.

Okay, this is interesting. 

Does that mean if I'm a 10 handicap and I want to play against a scratch golfer, I should play that scratch golfer at a higher slope/rating course. Because although I'll likely shoot a higher score relative to my handicap, the scratch will likely shoot a higher score relative to their handicap as well, but won't get the adjustment due to the slope/rating? 

Or am I thinking about that totally wrong??? 🤷‍♂️

My bag is an ever-changing combination of clubs. 

A mix I am forever tinkering with. 

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On 11/16/2023 at 8:16 PM, iacas said:

No, they didn't score better. They got slightly better differentials.

  • 66/112 @ 13.2 = 79.3
  • 75/142 @ 10.7 = 83.5

I understood that, I guess I should’ve said, “relative to the course, they scored better” (ie their differentials were better). It’s still interesting to me that their differentials were better on more difficult courses, but now that you posted that, with reflection I see that in my own scores. 

 

28 minutes ago, ChetlovesMer said:

Okay, this is interesting. 

Does that mean if I'm a 10 handicap and I want to play against a scratch golfer, I should play that scratch golfer at a higher slope/rating course. Because although I'll likely shoot a higher score relative to my handicap, the scratch will likely shoot a higher score relative to their handicap as well, but won't get the adjustment due to the slope/rating? 

Or am I thinking about that totally wrong??? 🤷‍♂️

That’s how I’m interpreting it

Driver: :callaway: Rogue ST  /  Woods: :tmade: Stealth 5W / Hybrid: :tmade: Stealth 25* / Irons: :ping: i500’s /  Wedges: :edel: 54*, 58*; Putter: :scotty_cameron: Futura 5  Ball: image.png Vero X1

 

 -Jonny

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This is why I moved up from the back tees at my regular courses. I score about the same because the difference in distance is not the predominant factor in my scoring and my index is higher now which more accurately reflects my playing ability.

Bill

“By three methods we may learn wisdom: First, by reflection, which is noblest; Second, by imitation, which is easiest; and third by experience, which is the bitterest.” - Confucius

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11 hours ago, Ty_Webb said:

In my experience, the higher slope/course rating courses the tees are frequently up from where they "should" be. I'm guessing very few people adjust their course and slope ratings for tees not being all the way back. For example, at Bethpage Black, the blue tees are 77.5/155. They are based on a yardage of I think 7,468. I have never seen the blue tees all the way back on seven of the holes in perhaps 40 playings. My guess is some of this at least is driven by where the tees are. 

I suspect you are correct. At the courses here in Southern California, it’s very common to see the tees moved forward on several holes. If I were to play 10 rounds at a random sampling of courses, my guess is that the back tee markers would be “correct” (say, within 25-30 yards of the course yardage) on two of them. Often the difference is well over 100 yards. 
 

I adjust within reason, but there are times when I don’t. For example, if the difference between blues and the next set down is substantial and I think the score is unlikely to count towards my 8, I’ll probably just post it as a blue tee score. This shaves a few off my “anti-cap” and probably affects the data above as well. My hunch is that most golfers don’t adjust at all.

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15 hours ago, Ty_Webb said:

In my experience, the higher slope/course rating courses the tees are frequently up from where they "should" be. I'm guessing very few people adjust their course and slope ratings for tees not being all the way back.

That happens far less often than your anecdata implies. It would show up in the PCC and even if it didn't rise to that level, in the scores expected versus posted. Courses that do this regularly are flagged and re-rated. It has not happened much at all.

15 hours ago, Ty_Webb said:

The other driver here would be where players' strengths lie. I tend to wind up with better differentials on higher slope/course ratings, just because pars on hard holes I find easier than birdies on easy holes.

Same reason people under-estimate the scores PGA Tour players would shoot on their scores. Length doesn't scale up the scores as linearly as it scales up the CR/Slope.

15 hours ago, Ty_Webb said:

I'd also be curious how much data there is in the tails here.

Right, so don't look at the tails. Not many 10s are playing 75+ tees either. Look at the chunk in the middle. The trend is still there.

3 hours ago, Big C said:

Often the difference is well over 100 yards. 

https://www.usga.org/content/usga/home-page/handicapping/roh/Content/rules/Appendix G Golf Course Course Rating Slope Rating.htm

Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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  • 2 weeks later...

This is interesting data and possibly related to a scenario for a specific course in Florida that I play.  When I play the 6200 yd tees there (70 CR), I end up having to lay up with a hybrid or 4i on most of the par 4/5 holes (due to water or sand).  However, from the 6800 yd tees (73 CR), I can hit driver on almost all of the par 4/5 holes.  So, the approach shots end up being similar regardless of 6200 vs. 6800, but I'm sacrificing ~40 yards of distance off the tee (though, with slightly better dispersion with 4i/hybrid).  My diff tends to be 2-3 strokes higher from the 6200 yd tees vs the 6800 yd tees.

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4 hours ago, MK4 said:

This is interesting data and possibly related to a scenario for a specific course in Florida that I play.  When I play the 6200 yd tees there (70 CR), I end up having to lay up with a hybrid or 4i on most of the par 4/5 holes (due to water or sand).  However, from the 6800 yd tees (73 CR), I can hit driver on almost all of the par 4/5 holes.  So, the approach shots end up being similar regardless of 6200 vs. 6800, but I'm sacrificing ~40 yards of distance off the tee (though, with slightly better dispersion with 4i/hybrid).  My diff tends to be 2-3 strokes higher from the 6200 yd tees vs the 6800 yd tees.

Depending on how far you hit certain things, the placement of certain hazards, etc. stuff like that can definitely lead to differences in scores.

Often, playing from forward tees, people don't improve their scores by much because they hit driver too often and hit it into more trouble than they should.

Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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9 minutes ago, iacas said:

Often, playing from forward tees, people don't improve their scores by much because they hit driver too often and hit it into more trouble than they should.

Very fascinating and makes complete sense.  Makes me wonder: if a person wants to ‘game’ their handicap before a tournament, could they play tees that are sub-optimal for their distance to produce higher diffs (e.g., moving to forward/easier tees that require forced lay-ups, for example)?  Conversely, if a person wants to lower their handicap, the data above indicates that they may want to play longer/harder courses (assuming no hazard issues like above, such as, for example, forced carries from back tees that are impossible for a person’s length).  

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3 minutes ago, MK4 said:

Very fascinating and makes complete sense.  Makes me wonder: if a person wants to ‘game’ their handicap before a tournament, could they play tees that are sub-optimal for their distance to produce higher diffs (e.g., moving to forward/easier tees that require forced lay-ups, for example)?  Conversely, if a person wants to lower their handicap, the data above indicates that they may want to play longer/harder courses (assuming no hazard issues like above, such as, for example, forced carries from back tees that are impossible for a person’s length).  

Within the rules (because you could always sandbag/cheat to raise your index): yes, you could play as far forward as is rated, try to play your best, and the charts and data say that you'll likely score worse than if you played back.

This is why I didn't like that our PAT was played from about 6500 yards (IIRC). More would have passed, I think, if it was at 7100yards.

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Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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11 hours ago, iacas said:

the charts and data say that you'll likely score worse than if you played back

Another thing that I thought of this morning: the chart that you posted is the average differential for all 10 handicap golfers.  I wonder if the average diffs would vary for different types of 10 HCs - e.g., would a 10 HC whose strength is driver/approach fare differently than a 10 HC whose strength is short game/putting?  I honestly have no idea, but it's an interesting idea.

The reason I thought of this is because of the situation I described above (e.g., Florida course with forced layups from 6200 yd tees due to hazards).  I think a person whose strength is driving distance would be more hurt by forward tees that necessitate a layup.  

I've spent far too much time thinking about this post, but it is really cool to see the numbers.  

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4 hours ago, MK4 said:

Another thing that I thought of this morning: the chart that you posted is the average differential for all 10 handicap golfers.  I wonder if the average diffs would vary for different types of 10 HCs - e.g., would a 10 HC whose strength is driver/approach fare differently than a 10 HC whose strength is short game/putting?  I honestly have no idea, but it's an interesting idea.

Sure, but not as much as most people think. People are often not nearly as unique as they feel they are. An outlier is an outlier for a reason: outliers aren't 45% of the people. 😄

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Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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19 hours ago, iacas said:

This is why I didn't like that our PAT was played from about 6500 yards (IIRC). More would have passed, I think, if it was at 7100yards.

What did you need to shoot? Is it something like within 5 of the course rating, or some kind of differential requirement?

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2 minutes ago, Ty_Webb said:

What did you need to shoot? Is it something like within 5 of the course rating, or some kind of differential requirement?

15 over the course rating or less (two rounds).

So our rating was 69.7, which is 139.4, so we had to shoot 154.4 or better. Since you can't get 0.3 strokes, that's 154. I'd have rather played it back a set of tees or two.

Erik J. Barzeski —  I knock a ball. It goes in a gopher hole. 🏌🏼‍♂️
Director of Instruction Golf Evolution • Owner, The Sand Trap .com • AuthorLowest Score Wins
Golf Digest "Best Young Teachers in America" 2016-17 & "Best in State" 2017-20 • WNY Section PGA Teacher of the Year 2019 :edel: :true_linkswear:

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3 hours ago, iacas said:

15 over the course rating or less (two rounds).

So our rating was 69.7, which is 139.4, so we had to shoot 154.4 or better. Since you can't get 0.3 strokes, that's 154. I'd have rather played it back a set of tees or two.

That is interesting - since you don't get any additional leeway for slope, you should want a low sloped course I would think, although granted at professional level, slope should have less effect than most and then the extra couple of shots from the course rating help more than the added distance hinders. 

To bring this back to the topic, the thing I find is my range of scores doesn't move very much with slope. So on a short course with a low slope and low course rating, my scores might range by 10-12 shots (for the most part - there will be outliers for sure, but my game tends to be relatively tight). On a long course with a high slope and high course rating, my scores still range by around 10-12 shots. Because of the way slope works, my differentials are much tighter on higher sloped courses. Playing Bethpage Black for example, the blue tees are par 71, CR 77.5 and SR 155. It's pretty tough to get up to even a 6 differential around there. I play a par 71, CR 69.2, SR 124, I can very easily get a 8 or 9 differential. 

Slope is a measure of variation in scores based on variation of skill level. I think it works pretty well to do that. That doesn't carry to variation in scores based on variation of how well I play on a given day (at least for me). I guess what it boils down to is how well or badly I play has little to do with the course I'm playing. If I'm missing three foot putts, it doesn't matter whether the course is long and difficult or short and easy. I'm still missing three foot putts. 

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