Strokes Gained – A Quick Primer

If you’re not familiar with Strokes Gained, then this should get you up to speed enough to follow my conversation tracking my statistical progress.

The strokes gained idea took off based on work done by Mark Broadie. He wrote a book on the topic called Every Shot Counts. I highly recommend it. It may get a little too numbersy for some, but the conclusions drawn from the statistics are pretty eye opening, even if they should be taken with some skepticism. They’ll also help to better understand all the strokes gained talk that is starting to happen on the PGA Tour broadcasts.

The basic premise of strokes gained is quantifying how you did on a shot when compared to some population of golfers. With the availability of shotlink data provided by the PGA Tour, there is a lot of data for their population of golfers. Therefore the PGA Tour is the easiest population to use as a baseline for performance.

Here is an example of how strokes gained works… From 140 yards to the hole in the middle of the fairway, the PGA Tour averages 2.91 strokes to hole out. Or in other words. If I made every tour player play the same shot from that distance, they would average a score of 2.91.

Therefore, if you get up and down from that location (ie. take 2 strokes to finish from 140 yards) you have effectively gained 0.91 strokes (2.91 – 2 = 0.91) on the tour average. Conversely, if you take 3 strokes you have lost 0.09 strokes (2.91 – 3 = -0.09) to the tour average.

Now the average number of strokes changes depending on the lie… That same 140 yards would take 2.97 strokes from a tee (surprising!), 3.15 strokes from rough, 3.22 strokes from sand, or 3.8 strokes for some sort of recovery shot as the tour pro average.

The table changes slightly for putting, but the same principle applies. PGA Tour players are 50% in making putts from 8 feet. Another way to say this is that the average score for a Tour Player from 8 feet is 1.5 strokes. Therefore, everytime a Tour Player (or you) makes an 8 footer, he gains 0.5 strokes on the field. Everytime the tour player misses, 0.5 strokes is lost to the field.

Let’s look at an in depth example. Let’s say I made a 2 from our position of 140 yards in the fairway. Overall I definitely gained strokes, but where did I gain the strokes? There are many ways to make a 2 from 140 yards. Let’s consider the following 3 ways:
   1) I stuff a 9 iron to 3 feet and then convert the putt,
   2) I hit a decent 9 iron to 15 fee and hole the remaining putt, or

   3) I don’t catch all of the 9 iron and leave it in a greenside bunker from 20 yards. I then hole the shot from the bunker.

To calculate the strokes gained on a specific shot is not incredibly difficult. You simply take the average number of strokes it would take to finish from the starting point of your shot, subtract the average number of strokes it would take to finish from wherever the ball ends up, and subtract 1 for the actual stroke taken.

The equation would look as follows:

 (Strokes Gained) = (Ave. # Shots to Finish from Before) – (Ave. # Shots to Finish from After) – 1

Returning to our 3 examples… Your intuition would be the following:
  1) You hit a great approach shot! Hardly needed to putt.
  2) You hit a decent approach shot, but a really good putt.

  3) You hit a terrible approach shot, but a miraculous save from the bunker.

Now using strokes gained we can calculate just how good each of those shots were. This becomes apparent in the next table:

Screen Shot 2015-05-06 at 9.53.31 PM

You can see that the great approach from scenario 1 was almost worth a full stroke on the field! The same is true of the putt in scenario 2. A great putt covered up a mediocre iron shot. In scenario 3, we hit a dreadful approach. However, the holed out sand shot was incredible, saving over 1.5 strokes on the field! So now we were able to quantify just what each shot meant, validating our intuition.
The next table shows how these numbers were calculated referencing the tables from Every Shot Counts.
Screen Shot 2015-05-06 at 10.34.42 PM

Keep in mind that these are averages. Not all lies are equal. The strokes gained does not take into account if the sand shot was plugged, or if the fairway shot was to a tucked pin over water vs. a receptive and wide open green with no wind. These are averages, so over volume data they are more or less accurate. They give you a pretty good idea of how you did vs. a solid reference. When tracked over time these stats can tell you what you are doing well and what you need to improve. For any given shot they can be slightly misleading. For instance, if I am standing on a golf course, just 20 yards from the pin but with a downhill lie to a tucked pin over a bunker and I hit a super flop to 10 feet… The strokes gained on that shot is (2.59 – 1.61 – 1) = -.02. This indicates that I lost 0.02 strokes to the field. However, that was a much more difficult shot than your average 20 yard pitch from the rough, so realistically I probably gained strokes on that particular shot. But again, over volume data and many shots, the averages work out to give a good gauge of short game competence.

One way to use this data is to keep track of your strokes gained for different situations. For instance, the PGA Tour has been reporting Strokes Gained Putting for a while now, but the stat can be used for other situations. I could look at my strokes gained for tee shots only, just approach shots into greens, or just look at strokes gained with my driver. By comparing these stats to the PGA Tour reference I can see where I am strong and where I am weak. This is what I plan to show on this blog.

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