USGA 9-Hole Scores, Thoughts?

[downeyjr]

I play a lot of 9 hole golf as I don't have a ton of time to play 18 and it allows me to get onto the course more than just once a week.

Have posted 2x so far (39, 40), course has a 35/124 rating on the front 9. Under the old system this would have been a 7.88 differential combined score but under the current system I've posted a 9.6 and a 8.5.

To me it seems like posting 9 holes has gone from a way to get a vanity handicap to a way to sandbag.

[SteveLo]

I personally don’t post my 9 hole scores. I feel like a lot can change on a “back 9”. At least for my skill set & experience.

[downeyjr]

I'm fairly consistent front and back, and if anything I'm usually better on the back 9. If I didn't post my 9's I wouldn't have a handicap lol.

Trying to play more tournaments this year so new posting rules could end up helping me out I guess, just thinking USGA will need to tweak their algorithm to get a fairer picture. Could be a me thing though as I usually just stroll to the first tee from my car and bypass any sort of practice.

[Golf2Much]

Overall, I think the new WHS deals with 9 hole scores (and for when only 10-17 holes are played) are a better solution than combining 9-hole rounds or relying on net double bogeys for missed holes.  The use of expected score for the holes not played is based on what the player is expected to score over a specific number of holes of standard difficulty using the player's handicap index and a normal distribution of scores.  It's not specific to any player.  The good news is that the math is "behind the curtain" and the average golfer doesn't have to worry about it.  

The new system helps provide more consistency in scoring.   In the past, you could play two nine-hole rounds over an extended time under completely different playing conditions.  Missed holes were assigned a net double bogey.   Does that better represent one's true demonstrated ability?  The new system also gives more flexibility, makes it easier for people just starting to establish a handicap and automates something that many would find confusing.  As someone who involved with my club's handicaps, it's amazing after four years some people still do not get the net double bogey maximum score for posting purposes.

As far as leading toward more sandbagging, the way that 9 hole scores or when 10-17 holes are completed will show up differently on a player's posted rounds.  I believe people will see (including the Handicap Committee) the number of holes played, the adjusted score for those holes along with the modified course rating, slope and adjusted differential for the estimated 18 hole round.  If there's something fishy going on with posting rounds with less than 18 holes completed, it should pop up and be easier to see.  

[downeyjr]

4 hours ago, Golf2Much said:

Missed holes were assigned a net double bogey. 

I think they were scored Net Par if you had to skip for a valid reason, which would be even worse. 

4 hours ago, Golf2Much said:

If there's something fishy going on with posting rounds with less than 18 holes completed, it should pop up and be easier to see.  

What I meant by sandbagging is that from what I've seen on my first couple of rounds posted of 9 holes, that even if I'm playing up to or a little bit better than my average, the differential from the 9 hole will not count. It is like auto-sandbagging if you play 9, and previously it was nearly a penalty (by lowering your handicap) to combine scores.

Just seems like they went from one extreme to maybe another, I think we may see some revisions to the differential calculations in a year or two for 9 and 10-17.

I have some tournaments coming up so not really complaining lol

[Golf2Much]

Yep, net par.   For some reason, I had net double on my mind.  

We're still in the early phases of this transition to the new methodology.  As more people post scores of 9-hole rounds, hopefully things will all level off and it will become less of an issue.  

[RoyF]

On 3/21/2024 at 7:43 PM, SteveLo said:

I personally don’t post my 9 hole scores. I feel like a lot can change on a “back 9”. At least for my skill set & experience.

The USGA requires that you post all rounds played, with a few exceptions, like scrambles, alternate shot, etc. Each 9 holes has its own rating, so the resulting affect on your handicap index is accurate (explained here and video here). Just something to consider...

While I don't agree with your decision, I admit that a rule I commonly violate is to use a different ball during a round. I might hit a Callaway Tour Soft on 1, lost it on 3 and pull a Titiest Pro V1 out of my bag. I never switch balls to putt or for a particular hole or shot, but I don't always stick to one specific ball during non-competition rounds. If a quality ball is on sale, I'll buy it. Now, during a tournament, I'm careful to use the same ball throughout.

Hmm, in looking up the USGA rule so I could reference it, I may have learned something. The One Ball Rule is actually Model Local Rule G-4 and it is a rule that Committees may choose to use, I didn't know that and I don't know if I've ever seen it stated for a tournament that the rule is being used, I just learned at some point that a One Ball Rule existed and thought it was a standard USGA rule. Perhaps I haven't been the habitual criminal that I thought I was.

Edited March 27 by RoyF

[Jonknowsgolf]

My first two 9 hole scores just posted last night from the men's league I play in. First impression is that they seem a little inflated. I am guessing that the algorithm will need some tweaking over time to get more accurate. I guess we're in the data collection phase now.

I like the idea, especially considering it never seemed like the combined scores gave a fair assessment of an 18 hole round. Playing conditions, course conditions and just day to day fluctuations in play had too much variation for 2 scores from different days, weeks, months, etc to give an accurate differential. It will be interesting to see how this new system works out. In the short run, I'm expecting some inflated handicaps..

[JJobu]

We have now had a month of posting 9-hole scores under the new system which is a decent sample size for my course as maybe 50% - 60% of the rounds posted by players in my group (25'ish players) are 9-hole scores rather than 18 and almost all of us play multiple times per week, every week. 

The general consensus seems to be that indexes feel inflated. That makes sense considering the Expected Differential for the 9-holes not played is based on an average for players in the same handicap range. It eliminates the possibility of a 9-hole differential ever being posted as 2x9-holes of better than average golf which I am not convinced is the best way to approach it. 

I am working under the assumption that the Expected Differential is an overall average for people in the same handicap range rather than an average of only the scores that counted for handicap purposes. It would be interesting to see if there would be any difference between an average 9-hole differential for the back 9 of 18 hole rounds when the score counted for the handicap calculation versus just the Expected Differential which is an average of all rounds(?).

At any rate, it seems like they are trying to make 9-hole rounds more comparable to 18-hole rounds but I am not sure they are approaching it the best way but of course I have no hard data to back that up.

Just off the top of my head I get the feeling that forcing players to post a minimum of the front 9 score and back 9 score for 18-hole rounds (versus allowing just the overall score) and then using each 9-hole score as a 9-hole differential would put things maybe more in line. ie. your index would be the best 16 of 40 x 9-hole differentials x 2. The overall 18-hole index then might need to be multiplied by a small multiplier, like 1.02 for an 'out of thin air' example, so that indexes remain more in line with how they have been in the past. 

[Iamsecond116]

Another interesting component is front & back 9's may have different ratings - so how is that calculated here? The old system in my recollection would adjust appropriately as it took each individual 9-hole round by itself and then combined those to come up with an 18-hole differential. Definitely lead to opportunities to lower your handicap by combining scores from different courses. 

In the current system, how are they able to take a score from the front 9 with a 125 slope and project it to the back 9 with a 135 slope?  I haven't seen any info on this... food for thought.

[JJobu]

1 hour ago, Iamsecond116 said:

Another interesting component is front & back 9's may have different ratings - so how is that calculated here? The old system in my recollection would adjust appropriately as it took each individual 9-hole round by itself and then combined those to come up with an 18-hole differential. Definitely lead to opportunities to lower your handicap by combining scores from different courses. 

In the current system, how are they able to take a score from the front 9 with a 125 slope and project it to the back 9 with a 135 slope?  I haven't seen any info on this... food for thought.

Edit: I do not think what I typed below is quite correct. See my post lower down in the thread.

I assume using the Expected Score and then the normal formula to calculate the remaining 9-holes not played.  For a slope of 125 the formula would be...

ie. Handicap Differential = (Expected Score - back 9 Course Rating) x (113 / 125) = X

Edited May 15 by JJobu

[downeyjr]

I would really love to see how the 9 hole scores are calculated, I have to assume the it is extrapolating an expect 18 score based on a constant slope/rating from the 9 you have played. 

[cnosil]

5 minutes ago, downeyjr said:

I would really love to see how the 9 hole scores are calculated, I have to assume the it is extrapolating an expect 18 score based on a constant slope/rating from the 9 you have played. 

https://www.usga.org/content/usga/home-page/handicapping/world-handicap-system/2024-revision/2024-treatment-of-9-hole-scores-FAQ.html
 

you can also get the 9 hole ratings for front and back here: https://ncrdb.usga.org

 

[JJobu]

46 minutes ago, downeyjr said:

I would really love to see how the 9 hole scores are calculated, I have to assume the it is extrapolating an expect 18 score based on a constant slope/rating from the 9 you have played. 

My understanding is that it uses an expected score based on an average score, for someone of your index, for the 9-holes not played and using the slope and rating for the 9-holes not played. 

 

edit: in short it adds the expected remaining 9-hole score to the score of the 9-holes you did play and then using that 18-hole score to calculate the differential.

 

My last 2 scores are :

80 for an 18-hole round with a differential of 11.0

39 for a 9-hole round with a differential of 11.0 (which means the Expected Score for someone at my index for the back 9 at my course is a 41). ie. a 18-hole round of 80 is the same 11.0 differential. 

 

Edited May 15 by JJobu
added content

[downeyjr]

I'm trying to play around in excel to figure how they are coming up with the expect score.

I can get close but nothing is consistent when I compare to my scores.

[DaveP043]

4 hours ago, downeyjr said:

I would really love to see how the 9 hole scores are calculated, I have to assume the it is extrapolating an expect 18 score based on a constant slope/rating from the 9 you have played. 

No, a DIFFERENTIAL is the number after any effect of Course Rating and Slope have been accounted for, so your Expected Differential has nothing to do with the CR and Slope for the course you just played 9 holes on.  It is essentially an average differential for all golfers with the same Handicap Index.  Remember that your AVERAGE differential is higher than your Handicap Index, since 60% of the scores are thrown out when calculating a HI.  I did a quick evaluation based on scores at my club, and the Expected Diff is about half your Index (i.e. for 9 holes) plus a constant ranging from about 1.2 to 1.8.  The lower your index, the lower that constant, so 1.2 would apply to scratch players, 1.8 would apply to 20+ handicappers..  This equates to an average 18-hole differential of about 2.5 to 3.5 strokes over "net par", a pretty reasonable estimate for a player's average score.

[JJobu]

17 hours ago, downeyjr said:

I'm trying to play around in excel to figure how they are coming up with the expect score.

I can get close but nothing is consistent when I compare to my scores.

We really can't get at the formula unless we had a large number of scores and knew the exact index of the player when they posted the score. It is taking the actual 9-hole differential and adding another differential for the other 9-holes which is the average differential (not score) for someone of the same index at the time of posting. 3 players with indexes of 10.1, 10.2 and 10.3 shooting the same score, from the same tees, might produce 3 different differentials. 

For my course the differential produced for 9-holes played is like I shot 41 on the 9-holes not played. Doesn't matter if I played the front 9 or back 9. Adding 41 to any of my 9 holes scores and comparing that 18-hole score differential to the 9-hole differential when posting gets me to within +/- .3 for almost all scores with one exception where the variance is +/- .5. 

Of course as my index changes more so should the expected differential for the 9-holes not played.

 

[DaveP043]

1 hour ago, JJobu said:

We really can't get at the formula unless we had a large number of scores and knew the exact index of the player when they posted the score

You don't need a ton of scores, I did my evaluation with a couple dozen.  As I said earlier, the Expected Diff for 9 holes is half your index plus 1.2 to to 1.8, 1.2 for lower handicappers, 1.8 for higher.  it seemed pretty linear within that range.  I didn't have any REALLY low or high handicappers, but it seems likely that the "added constant" could go higher or lower.

[downeyjr]

13 minutes ago, DaveP043 said:

You don't need a ton of scores, I did my evaluation with a couple dozen.  As I said earlier, the Expected Diff for 9 holes is half your index plus 1.2 to to 1.8, 1.2 for lower handicappers, 1.8 for higher.  it seemed pretty linear within that range.  I didn't have any REALLY low or high handicappers, but it seems likely that the "added constant" could go higher or lower.

I have 12 scores, ranging from hitting my CH to...pretty bad. I also added a friends that shot 3 shots under CH (9 hole diff would have been 0.8 in old calculation) and the sample from USGA.

I also have my handicaps, the sample handicap, and my buddies handicap at the time.

I don't think it is a constant, but yes what you mention does get you pretty close. Unfortunately I was an polictical econ major and not a math major.

 

[JJobu]

4 hours ago, DaveP043 said:

You don't need a ton of scores, I did my evaluation with a couple dozen.  As I said earlier, the Expected Diff for 9 holes is half your index plus 1.2 to to 1.8, 1.2 for lower handicappers, 1.8 for higher.  it seemed pretty linear within that range.  I didn't have any REALLY low or high handicappers, but it seems likely that the "added constant" could go higher or lower.

Looking at it your way of explaining it is my math off here? It doesn't seem to be the same each time. I understand there would be minor differences as my index fluctuates up or down a moderate amount but with only a range of 10.7 to 10.9...

They are probably rounding at some point or maybe multiple points.

 

4/16 index = 10.7 (half is 5.35)
score of 42 on a 34.0/114 course = 14.5 differential
(42 - 34.0) * (113/114) = 7.929
7.929 + 5.35 = 13.279
14.5 - 13.279 = 1.22 added to half my index

 

5/8 index = 10.8 (half is 5.4)
score of 39 on a 33.7/121 course = 11.8 differential
(39 - 33.7) * (113/121) = 4.949
4.949 + 5.4 = 10.349
11.8 - 10.349 = 1.45 added to half my index

 

5/16 index = 10.9 (half is 5.45)
score of 40 on a 34.0/114 course = 12.8 differential
(40 - 34.0) * (113/114) = 5.947
5.947 + 5.45 = 11.397
12.8 - 11.397 = 1.40 added to half my index

 

 

 

[DaveP043]

2 hours ago, JJobu said:

Looking at it your way of explaining it is my math off here? It doesn't seem to be the same each time. I understand there would be minor differences as my index fluctuates up or down a moderate amount but with only a range of 10.7 to 10.9...

They are probably rounding at some point or maybe multiple points.

4/16 index = 10.7 (half is 5.35)
score of 42 on a 34.0/114 course = 14.5 differential
(42 - 34.0) * (113/114) = 7.929
7.929 + 5.35 = 13.279
14.5 - 13.279 = 1.22 added to half my index

5/8 index = 10.8 (half is 5.4)
score of 39 on a 33.7/121 course = 11.8 differential
(39 - 33.7) * (113/121) = 4.949
4.949 + 5.4 = 10.349
11.8 - 10.349 = 1.45 added to half my index

5/16 index = 10.9 (half is 5.45)
score of 40 on a 34.0/114 course = 12.8 differential
(40 - 34.0) * (113/114) = 5.947
5.947 + 5.45 = 11.397
12.8 - 11.397 = 1.40 added to half my index

The last two seem about what I'd suspect, that 0.01 column might produce a little rounding different, but its close to 0.5*HI + 1..4.  The first seems out of whack by something like 0.2.

[JJobu]

15 hours ago, DaveP043 said:

The last two seem about what I'd suspect, that 0.01 column might produce a little rounding different, but its close to 0.5*HI + 1..4.  The first seems out of whack by something like 0.2.

I checked a few others and all seem to fall into the 1.4 to 1.45 range added to half my index at the time of posting.

With the first one from my last post I think the reason for the difference is I had a score the day before that did not trigger an index calculation the next day. Either I forgot to post the day of or the system was delayed in adding the revision, both of which have happened before. So the system may have gone back and adjusted based on the delayed posting/revision and my index would have been 10.4 not 10.7 which would make that one 1.371 added to half my index.