Cool Golf Analytics: Putting for Dough

In 2009 Wharton economists Devin Pope and Maurice Schweitzer published a paper titled “Is Tiger Woods Loss Averse? Persistent Bias in the Face of Experience, Competition, and High Stakes.” Pope and Schweitzer used data from 239 PGA tournaments between 2004 and 2009, concentrating on 2.5 million putts attempted by 421 professional golfers who each made at least 1,000 putts.

Their study explores “loss aversion” — a bias in decision-making that is an important element in the growing field of behavioral economics, which explores how human psychology impacts markets and business. “This research provides evidence that people work especially hard in order to avoid losses,” said Pope. In the current economy, he adds, “a lot of people … are very determined to get out of the loss domain and return to where they were a couple of years ago.”

To focus on the issue of loss aversion, the researchers examined the putts in the context of the par set for each hole. According to the researchers, the par number creates a reference point that clearly distinguishes a loss from a gain. On their scorecards, golfers circle holes they score under par. If they shoot over par, the score is framed in a dreaded square. “Though golfers should only care about their overall tournament score, golfers may be influenced by the salient, but normatively irrelevant, reference point of par when they attempt putts,” the authors write.

Most of the putts in the data were for par (47%) or birdie (39.8%). The approach to each hole taken by golfers, relative to par, provides a way to measure loss aversion. Pope and Schweitzer used the PGA data to determine whether a golfer was playing it safe by making a putt that would end up just in front of the hole, in order to set up a sure next shot. Using data measuring the force of a stroke and position of a ball before the putt, the researchers determined that, on average, golfers make their birdie putts approximately two percentage points less often than they make comparable par putts. “This finding is consistent with loss aversion; players invest more focus when putting for par to avoid encoding a loss,” the researchers wrote.

Schweitzer notes that the behavior reflects the bias toward avoiding loss — in this case, missing par and scoring a bogey — over the potential to score more in the overall tournament, which is what ultimately matters. “Loss aversion is the systematic mistake of segregating gains and losses — evaluating decisions in isolation rather than in the aggregate — and over-weighting losses relative to gains.”

As interesting as this analysis is, I was equally intrigued by the way the PGA Tour collects this data. According to the PGA website, the database is called ShotLink and they described it thus:

So why are all of those people at PGA TOUR events walking around with hand-held Palm devices and laser guns near the course?

Don’t be alarmed, it’s not a bad thing. In fact, the data that the approximately 250 volunteers a week gather using hand-held computers and lasers actually brings fans closer to their favorite players.

Developed in conjunction with IBM, the TOUR’s Official Worldwide Information Technology Partner, this data-collecting system is known as ShotLink. The idea for ShotLink formed in 1997 after the TOUR realized an update was needed to its old system, which was based on technology that was 10 years old. ShotLink was introduced at the 2001 Buick Classic and became widely used at the start of the 2002 season.

Originally intended to catalogue and save statistical information for historical purposes, the data collected is now also used by print journalists, broadcasters,’s TOURCast application and even golf course superintendents to assist with their work.

“The main purpose of ShotLink is to gather pertinent data information with regards to the players, like getting yardages, stats and historical data that we can archive and have for future years,” said Jack White, director of ShotLink for the PGA TOUR. “The side benefits are that it also enhances the broadcast and is used in the media.”

White also noted that, because ShotLink can directly pinpoint where the most shots land on a certain hole, golf course staff can tinker with layout. For instance, if a par 5 has been reached easily by most players in two shots, tournament officials might change future hole placements to make it more difficult.

Players themselves benefit from the data, as their personal statistical information is now more reliable and readily available to them. In 2004, a program was developed so TOUR members can compare stats from different time periods. This might help, say, Tiger Woods, who would like to see how his stats looked before and after his most recent swing change.

ShotLink is used on all three Tours for approximately 102 tournaments a year. To put this complex ShotLink system in place, each course the TOUR plays was mapped, along with nine holes for Champions Tour events. Using Global Positioning System (GPS) devices, different layers and elevations were recorded to denote the greens, fairways, bunkers, water, rough, trees and other course elements.

This map of the course serves as a background for figuring out the distances between two points, such as the tee and where a player’s first shot lands.

That’s where the volunteers come in.

“The system doesn’t work without the volunteers. The entire ShotLink system is run by volunteers,” said White. “We have staff onsite who help the volunteers in terms of training and troubleshooting. If a piece of equipment goes down, we will either get it back up and running or replace it with one that works properly. But the entire system is run by volunteers.”

Approximately 10,000 volunteers a year help with the gathering of ShotLink data. A walking scorer accompanies each pairing and must have some knowledge of golf, as they use the Palm device to record information on the lie of the ball, which player hit each shot, the scores at the conclusion of the hole and other pertinent data. This information is sent to the ShotLink trailer on site, as well as the laser operator volunteers.

There are two different types of laser operators. The fairway volunteer has a slightly easier task, as they point a trigger-operated laser at each player’s ball and the system then automatically triangulates the exact location of the ball. Fairway operators are always in touch with the ShotLink trailer and have access to the data from the walking scorers, so within seconds they know which player’s shot they are recording.

Two other laser volunteers are needed for each hole, but their job is somewhat more difficult. The pair, seated on a platform several feet above the green, work as a team to gather accurate information on shots hit close to the hole. One works the “survey grade” laser while the other keeps up communication with the trailer and makes observations regarding play on the course.

ShotLink is highly precise, as the accuracy on the fairway is within a foot and within a centimeter on the green.

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