Historical handicap analysis

Course Rating minus par and the historical WHS comparison

Why a change in Course Handicap could affect the adjusted score used for handicapping, even when the gross round was the same.

Tonny GottliebCEO, How Many Strokes6 February 2023

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For a current starting point, read Course Rating, Slope and Par and national WHS procedures.

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• The World Handicap System “Excluding CR minus Par” vs. “Including CR minus Par”. What does it mean for the Score Differential?

The World Handicap System (WHS) brought together six former handicapping systems under the joint oversight of the USGA and The R&A. Introduction began in 2020, with implementation responsibilities and national choices handled by authorised associations.

WHS aims to make a Handicap Index more portable and help golfers of different abilities play together. That shared framework does not remove the need to use the ratings, acceptable formats and submission procedures that apply at the course and under the responsible authorised association.

A Handicap Index is converted for the course and tees being played. For a record containing 20 Score Differentials, the basic Handicap Index calculation uses the lowest eight of the most recent 20, subject to other applicable WHS adjustments. It is not an average of gross scores or a recalculation based only on the latest round.

The USGA and The R&A oversee the global framework. Authorised national associations implement and administer it within their jurisdictions.

What the unified system aimed to offer

• Simplifying the handicapping process and making it more consistent and understandable for all players by using a single, unified measure
• Allowing players to easily transfer their handicaps from club to club and country to country
• Making golf more inclusive and accessible to a broader range of players by creating more opportunities for golfers of all skill levels to play for recreation and competition
• Enabling non-club member golfing communities to have access to their handicap indexes
• Enable golfers of different abilities to play and compete on a fair and equal basis, in any format, on any course, anywhere around the world
• Be easy to understand and implement without sacrificing accuracy
• Meet the varied needs and expectations of golfers, golf clubs and golf authorities all around the world and be adaptable to suit all golfing cultures

Slope Rating and Course Rating

Slope Rating expresses the relative difficulty of a set of tees for players who are not scratch golfers compared with scratch golfers.

Course Rating represents playing difficulty for a scratch golfer under normal course and weather conditions. Bogey Rating represents difficulty for a bogey golfer. Both relate to a particular set of tees; Course Rating is not simply par or one universal number for the course.

Slope Rating is derived from Bogey Rating minus Course Rating, multiplied by the applicable factor.

Course Handicap and Score Differential have different jobs

The Handicap Index is converted to a Course Handicap for the selected course and tees. For the 18-hole calculation including Course Rating minus par:
Course Handicap = (Handicap Index × Slope Rating / 113) + (Course Rating − Par)
Playing Handicap is the separate allowance-adjusted figure for a form of play. Follow the authorised association’s rounding procedure, retaining the unrounded Course Handicap through the calculation where required.

Course Handicap uses Handicap Index, Slope Rating and, in the formula examined here, Course Rating minus par. Playing Conditions Calculation (PCC) belongs to the Score Differential calculation; it is not an additional Course Handicap input.

The historical calculation without Course Rating minus par

The historical comparison used the former Great Britain and Ireland calculation without Course Rating minus par. That description explains the old diagrams; it is not current instructions for a country.

CONGU refers here to the earlier Great Britain and Ireland implementation. Check your authorised association’s guidance for today’s procedure.

The calculation including Course Rating minus par

The alternative calculation includes Course Rating minus par as well as Handicap Index and Slope Rating. It is shown here as a mathematical comparison, rather than a current country-by-country map.

How the Score Differential enters the record

For an 18-hole Score Differential, the usual formula is:
(113 / Slope Rating) × (Adjusted Gross Score − Course Rating − PCC)
The adjusted gross score can include the net-double-bogey limit for handicapping. The difference explored below arises through stroke allocation and hole-score adjustment in the historical examples, rather than through two different Score Differential formulas.

Why the historical comparison mattered

The short answer is YES; it does matter. If the players always play in their own country and never in a country that uses the opposite system, then maybe not that much, but still.

A worked comparison

Let’s look at an example.

Two players in Ireland are both members of the same club. The club has a moderate variance in difficulty (Slope Rating 114-125). In some cases, a club may have a wider difference (Slope Rating 110-150).

One player has a handicap index of 4,0 and is playing off back tee Blue 6742 yds. The player received a course handicap of 4 when playing inside the CONGU:

When “Excluding Course Rating minus Par”, the player has 4 received strokes no matter what tee the player chooses. Had the player been using “Including Course Rating minus Par” to calculate the Course Handicap, the received strokes would have been 6, so 2 more strokes if the player was outside the CONGU.

The other player has a handicap index of 18,0 and is playing off short tee Yellow 5622 yds. The player received a course handicap of 18 when playing inside the CONGU:

Had the player been using “Including Course Rating minus Par” to calculate the Course Handicap, the received strokes would have been 15, so 3 fewer strokes if the player was outside the CONGU.

If the player were playing from Blue tee, the received strokes would have been 22.

Note how a player receives more strokes from blue when “Including Course Rating minus Par” compared to “Excluding Course Rating minus Par” and fewer when playing a shorter tee.

Compare the two worked examples

Hcp 4.0 player of blue tee. The player shoots 81.

When comparing two identical rounds but using the two different calculations, it becomes clear that the score differential in some cases can be very different. The scores have been adjusted to hit the adj. Net Double Bogey to illustrate this more clearly.

The Score differential is used when calculating the best 8 out of the last 20 rounds to determine the player’s actual playing strength or hcp index.

If the same hole-score-adjustment pattern were repeated through the relevant scoring record, this example could lead to a lower Handicap Index under the historical calculation excluding Course Rating minus par. It is an illustration, not a prediction for every player.

Hcp 18,0 player of the yellow tee. The player shoots 98.

When comparing two identical rounds but using the two different calculations, it seems that the opposite is happening. Since the player has moved to a shorter tee with a different slope and rating, the outcome has been reversed. So, in this case, the player using “Excluding CR minus Par” will actually get a higher handicap than the player using “Including CR minus Par”.

With the different tees and hole-score-adjustment pattern in this example, the direction can reverse. If repeated through the relevant record, that pattern could produce a higher Handicap Index under the historical calculation excluding Course Rating minus par.

The two stated tee lengths differ by 1,120 yards: 6,742 minus 5,622. Tee choice should suit the player and the event; these examples are not advice to manipulate a Handicap Index.

How the difference varies across tees

Comparison between “Including CR minus Par” and “Excluding CR minus Par” for three different handicaps. Slope and Course Rating (CR) are paired in the most likely combination. For a complete mapping look at the 3D graph.

As the graph shows, there are courses/tees where the difference is minuscule, and the biggest difference is typically on the shortest or the longest tees.

3D graphs of all the combinations of Course Rating and Slope Rating for the two calculations for an HCP 18.0 Player. The jumps in the graphic are due to the Course HCP being rounded (click on the graph to zoom):

Net double bogey and the adjusted hole score

What the examples show

Upon further examination of the data, it may appear that there are only minor disparities between the two systems. This is especially true for players who typically play from the middle tees, where the variation is minimal. Additionally, for players who perform at or better than their handicap index, the differences between the systems become even less noticeable. So yes, there are cases where there are no differences whether you use “Including CR minus Par” or “Excluding CR minus Par”.
A 0.1 difference in a player’s handicap index could mean extra or fewer strokes in a game, which can make a difference in a competition.

The cross-border example reflects an earlier implementation. Use current course data and national guidance when submitting a score abroad.

In this historical example, a player returned 38 Stableford points from Spain and the score was recalculated as 32 at home. For a round played abroad today, record and submit the information your authorised association requires.

Indeed, there is plenty of room for discussion and discourse when it comes to this issue. This is a complex topic with many different perspectives and opinions, and it’s essential to keep an open mind and be willing to engage in a healthy and productive dialogue.