So what does Strokes Gained tell us about PGA TOUR Player Performance?
The PGA TOUR has recently begun publishing Strokes Gained – Putting statistics on its website. The PGA TOUR has not yet however endorsed the Strokes Gained (SG) methodology for use beyond the putting green. The PGA TOUR has however released the raw ShotLink data to a number of researchers. Mark Broadie is one of these researchers and has performed extensive SG analyses of all facets of the golf game (i.e. drives, approaches, chips, sand shots, putts, etc).
Due to the circumstances outlined above, GolfBrains will use this entry to first present highlights of Broadie’s comprehensive performance analysis and then present GolfBrains’ own analysis of the putting data.
The summary of Broadie’s work below is not intended to be a substitute for the real thing. GolfBrains highly recommends you read his paper “Assessing Golfer Performance on the PGA Tour (individual player analysis begins on page 16). As mentioned previously, GolfBrains feels this is by far the best paper written on SG to date.
Broadie’s Strokes Gained Analysis
Broadie analyzed ShotLink data from the years 2003 through 2010. He only included players with at least 120 rounds played during this period. These parameters yielded a population of 299 PGA TOUR golfers which were included in the analysis.
Broadie’s analysis yielded interesting insights regarding which facets of the game separated the elite golfers from the average golfers. Most notably, he debunked the “drive for show, putt for dough” myth. Broadie concludes “the contributions to total strokes gained are 72%, 11% and 17% for the long game, the short game and putting respectively” (with “long game” defined as shots over 100 yards from the hole and “short game” defined as shots under 100 yards from the hole, excluding putts).
In addition to highlighting the importance of the long game, Broadie’s work shines a spotlight on the dominance of Tiger Woods during this period. For the period, Tiger gained 3.2 strokes per round over the average tour player. Over the course of a four round tournament, this suggests that Tiger is nearly 13 shots better than the average PGA TOUR player. A comparison to the other top players during this period further highlights Tiger’s dominance. Luke Donald, the sixth best player during this period only gained 1.55 strokes per round. Said another way, there were only four players in the world (Jim Furyk, Vijay Singh, Ernie Els and Phil Mickelson) who gained at least half as many strokes per round as Tiger. Jim Furyk, the second ranked player from this period, was over a full stroke behind Tiger at 2.12 SG per round.
Breaking down Tiger’s SG into its component parts, we learn that, similar to other PGA TOUR golfers, Tiger’s overall SG can be explained in large part by his long game. Of Tiger’s 3.2 SG, 2.08 can be attributed to his long game, 0.42 to his short game and 0.70 to his putting.
The chart below, shows Tiger’s total SG and SG components by year.
GolfBrains Strokes Gained – Putting Analysis
Rather than relying on Broadie’s work, this section relies on 2011 PGA Tour Stokes Gained – Putting data as of September 12, 2011 for all 189 golfers reported by the TOUR. As the PGA TOUR does not publish Strokes Gained measures for the short game or the long game, rather than comparing the various facets of the game, this section will compare Strokes Gained – Putting statistics with traditional putting statistics.
It has been stated on this blog before, but at the risk of being pedantic, GolfBrains will restate that traditional putting measures have the drawback of mixing several components of the game. Traditional putting measures are based on the number of putts per round or per green in regulation. Therefore, players who hit approach shots closer to the hole will appear to be better putters than they actually are. Let’s consider an example. Golfer A has an average first putt distance of 20 feet from the hole while Golfer B has an average first putt distance of 30 feet from the hole. On average, both golfers need 1.8 putts to hole out. Traditional golf statistics will suggest that these golfers are equally adept putters. The truth is, and SG reflects that, Golfer B is a superior putter.
First let’s compare Strokes Gained – Putting with Putts Per Round. As shown by the scatter plot and accompanying linear regression line below, Strokes Gained – Putting and Putts Per Round are correlated. The negative slope of the regression line indicates that as Putts Per Round decrease, Strokes Gained – Putting increases. The coefficient of determination with a value of R = 0.543 suggests that 54.3% of the variance is explained by the model. In layman’s terms, 54.3% of Strokes Gained – Putting can be explained by Putts Per Round. This suggests that Putts Per Round is not without value; it explains over half of Strokes Gained. However, on the flip side, it’s not a great statistics as it only accounts for half of a players putting performance.
This shortcoming is highlighted by the measures for Kevin Na and Alexandre Rocha. Kevin Na’s 27.78 Putts Per Round is the second lowest total on the PGA TOUR. Kevin Na is an excellent putter, but Strokes Gained tells us that he’s not as good as his Putts Per Round statistic suggests; there are in fact 19 better putters on the PGA Tour. Conversely, Rocha is a much better putter than his Putts Per Round statistics suggest. Ranking him in the 185th spot, Rocha’s Putts Per Round suggest that he is one of the worst putters on the PGA TOUR. The truth is he is a better than average putter. He gains 0.168 strokes per round by virtue of his above average putting.
Putts Per Green In Regulation (GIR) was introduced in an attempt to reduce the distortions inherent in the Putts Per Round statistic. Traditional thinking suggests that those players who hit a lot of GIR at a disadvantage when it comes to Putts Per Round; a golfer who misses a green in regulation and is chipping onto the green is likely to have a shorter, and therefore easier, first putt than a golfer who hit the GIR. Interestingly, a comparison with Strokes Gained – Putting suggests that Putts Per GIR is inferior to Putts Per Round in terms of explaining putting performance. In contrast with Putts Per Rounds which explains 54.3% of putting performance, Putts Per GIR explains only 47.1%.