In the recent years a new statistic has appeared all over the PGA tour – strokes gained. This mystical number is frequently talked of, raved about and discussed, but rarely understood. Here we will look at why it is a great stat and why it has zero bearing to your Sunday morning four-ball.

Image result for confused golfer

Traditionally golf statistics have clumped data together into set groups – fairways and greens hit or missed. These outcomes are then turned into a percentage, such as greens in regulation percentage.

The issue with this approach is that it doesn’t tell you a great deal about how that shot affected a player’s overall score. A missed fairway could be a foot into the semi-rough, behind a tree, or out of bounds. With a grouping approach all of these shots receive the same arbitrary value.

Strokes gained takes advantage of the PGA ShotlinkTM data that tracks every player’s shot hit during the season to within an accuracy of one inch. With this data we can calculate the average number of shots taken by a tour player to finish a hole from a given distance.

For example, the average number of shots for a PGA Tour player to finish a hole from 16 feet is 1.8 shots*. For a 1-foot putt the average is unsurprisingly 1, and for a 40 yard pitch from the fairway the average is 2.6 shots. This database of numbers forms the basis of any strokes gained statistic.

The next step in strokes gained is to take the player’s actual score away from the tour average for that same distance. If a player holes a 16-foot putt, he/she would gain 0.8 shots on the field.

The last step on the shots gained stats journey is where most get lost or confused. But stick with me, it’s actually quite simple and very powerful. What if they miss the 16-foot putt, how would we calculate the value of that putt? Or how can this be used to measure a 310 yard drive or an iron shot? To work this out we just need to head back to the database to find out the average shots taken by a tour player to complete the hole from where the ball finishes.

Back to our example above, imagine our player lags their 16-foot putt up to one foot. We know the start point was a tour average of 1.8, the end point was 1, and they have taken 1 shot to get there. The change in the strokes gained is 0.8 and they have taken 1 shot, therefore their strokes gained would be -0.2**, suggesting they lost -0.2 shots against the field.

In Broadie’s paper1 he gives an example of how this works during a round. Imagine a player is standing on the tee of a long par 3. The average number of shots taken to complete this hole is 3.2. The player hits their tee shot to 16-feet, leaving a putt for birdie. The start point for the shot was 3.2, minus the end value of 1.8 and minus the one shot taken this gives the tee shot a strokes gained value of +0.4***. This indicates they have gained +0.4 on the field, as a result of their tee shot.

All strokes gained stats for drives, iron shots, chips and putts can be added up in groups to give an indication of how a tour player is performing in each area of their game.

This approach adds a new lens to understand elite players performance. In 2010 Angel Cabrera had 26 putts in a round, but would have been grossly unhappy, as his average putt length was 9.6 feet. His putts gained stat was – 2.8 for the day. Conversely, in 2010 Ian Poulter had 32 putts at the Deutshe Bank championship, but gained + 2.3 on the field in putting, with an average putt length of 32.3 feet!

As you can see strokes gained is simple, very clever and yet no use to what you need to focus on to improve – why? The values for the start and end point of where your golf ball lands assumes you are already the level of a tour player. Last time I checked I wasn’t.

Recently people have been taking strokes gained data to push the importance of a great long game, as this is what commonly tells us the winner of a PGA Tour event. This is fine, as long as your pitching, chipping and putting is already at a +6 handicapper level.

So, in short, don’t neglect your short game. Those guys are good.

1.http://www.columbia.edu/~mnb2/broadie/Assets/strokes_gained_pga_broadie_20110408.pdf

NB: Please note this is a simplified explanation, with the aim of improving understanding. For further details on conditional dependence and adjusted shots gained please see the paper above.

Long hand calculations for examples above

*20% 1 putt and 80% 2 putt (less than 1% of 16 footers are 3 putts) (1.8 shots = (0.2 x 1) + (0.8 x 2) + (0.0 x 3)).

** Long hand SG = (SGi – SG+1) – 1 / SG = (1.8 – 1.0) – 1.

** Long hand SG = (SGi – SG+1) – 1 / +0.4 = (3.2 – 1.8) – 1.