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Crunch Time

Ten years after ShotLink transformed the stats game, the data revolution is ready to take on new ground. (Are you ready for strokes gained/tee to green?)

January 13, 2014

Who was the best driver of the ball on the PGA Tour in 2013? Was it Luke List, who led in distance at 306.3 yards? Jerry Kelly, who was tops in accuracy at 71.81 percent fairways hit? Wait, it must have been Graham DeLaet, who was No. 1 in the total driving stat that combines rankings in distance and accuracy. Actually, the best driver in terms of gaining the most advantage from where his tee shots finished was Bubba Watson. He led in strokes gained/driving, which is not an official PGA Tour statistic -- yet -- but is calculated by Columbia professor Mark Broadie, who helped the tour develop the strokes gained/putting stat.

Strokes gained/driving is just one example of advancements in statistical analysis in golf enabled by the PGA Tour's ShotLink system, which tracks the results of every shot at most tournaments and officially began 10 years ago at the start of the 2004 season. It took awhile to understand how best to utilize that mountain of data, but we have reached a point where a statistical revolution akin to those we've seen in other sports is well underway.

It can be argued that no sport needed a statistical advance more than golf. While traditional baseball stats like batting average and runs batted in are less than perfect measures of performance, golf's standard stats are more highly flawed. The old putting stats didn't account for the starting position on the green, and although they were replaced in 2011 by strokes gained/putting, that was only a first step. Driving accuracy is still measured by fairways hit, which counts a shot harmlessly in the intermediate cut the same as a ball out-of-bounds. Iron play remains tracked by greens in regulation, which doesn't factor in whether a player aims at the center of the green or fires at the flag. In addition, there's no good stat for the short game, and none of the traditional stats account for the often great difference in course difficulty in players' schedules.

Related: Embracing the stats revolution

New statistics aren't the only outgrowths of the ShotLink information. Players and coaches are beginning to see the usefulness of the data to target improvements in their games and strategies, in some cases bringing in a "stats coach" for analysis. The USGA mines the data to monitor developments regarding past and possible future equipment regulations. Architects use it in redesigning tour courses. Journalists can report the exact distance of putts rather than estimating. Golf fans can track the shots of any player in the field on pgatour.com.

shotlink

It all grew out of the PGA Tour realizing in the mid-1990s that its score- reporting system would need an upgrade for the 21st century. Hand-held digital devices rather than a pencil and paper were clearly the way to go for walking scorers to update leader boards more efficiently, and while they were at it someone had the forward-thinking idea of devising a system that could report the precise result of every shot hit on tour. It took years of development and a major financial investment to map each course and provide the resources for a laser measuring system at each tour event, but ultimately ShotLink was born, giving the tour an extensive database currently managed along with technology partner CDW.

Suddenly, the tour had new stats like percentage of putts made from various distances, average distance from the hole on approach shots from various yardage ranges, tendencies to miss left or right with tee shots and many more. But how to make some sense out of all those numbers? The tour's idea was to utilize the brainpower of America's university system, spreading word that customized ShotLink data would be made available to researchers.

Coincidentally, Broadie at about the same time had started his own research project analyzing exactly the same kind of data with a large group of amateur golfers who were tracking the results of every shot. His goal was to discern and quantify the differences between different levels of golfers, and his tool was the concept of strokes gained.

Related: What the numbers say about Tiger & Rory

In a nutshell, the idea is to compare the player's expected strokes required to hole out before and after each stroke. If he has improved his expected score, he has gained a commensurate amount (usually a fraction of a stroke), if he has worsened his expected score it goes down as a negative. For tour pros the expected score is determined by the tour average from a given position, based on reams of ShotLink data. An example would be a putt from just inside eight feet, which a pro is expected to make half the time. A make gives him .5 strokes gained, and a miss is -.5.

shotlink

Thanks to ShotLink, Broadie was able to expand his research to the tour-pro level. Meanwhile, a trio of Massachusetts Institute of Technology researchers (Douglas Fearing, Jason Acimovic and Steven Graves) combed six years of ShotLink statistics and published a paper in 2010 showing how strokes gained could be used to develop a new putting statistic.

"We knew there was a problem with the putting stat," says Steve Evans, the PGA Tour's senior vice president of information systems. "Ultimately, we realized there would be value in exposing the data to the academic community."

The MIT paper coined the term "strokes gained" instead of Broadie's original "shot value." In fact, by whatever name, the analytical tool is not new. Something along those lines was suggested in 1968 by Australians Alastair Cochran and John Stobbs. Peter Sanders developed a similar system called ShotByShot and started working with LPGA players in 1989 (he now works with PGA Tour players and has a program for amateurs), and L.M. Landsberger wrote a paper on the subject for the World Scientific Congress of Golf in 1994.

A few others were ahead of their time. Bob (Cowboy) Ming used to track the results of his players' shots with each club and analyze the data when he caddied on the PGA Tour in the 1990s. Annika Sorenstam became the top player in the women's game partly through recording the results of every shot she hit starting as a teenage amateur -- even as a pro, she would quickly jot down the information after each hole -- and inputting the data into a spreadsheet. Short-game instructor Dave Pelz got his start by meticulously recording shot-by-shot results for players he followed around the course in the late 1970s. His analysis of the data is what convinced players to start carrying a third (and eventually a fourth) wedge.

It was ShotLink that enabled full implementation, and strokes gained/putting marked the turning point in recognition and acceptance of advanced statistical analysis. But strokes gained doesn't need to stop at the green's edge. The calculation can be made for any shot, although it gets more complicated because there are more variables. The tour has been studying how to expand strokes gained since 2011, but is moving slowly and carefully in its consideration of the concept for drives, approach shots and short-game shots.

"The primary challenge is basically the tee shot versus the approach shot," says Evans. "If someone hits what appears to be a poor second shot based on the data, what portion of that is attributed to the tee shot and what portion to the approach shot?"

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