Using Performance to Predict Future Success

February 24, 2016
Jake Nichols

The first months of any season are a period of optimism. Any off-season changes to equipment, your swing, your technique, your putting grip, and so on are still new and full of promise. Most of the season remains in front of you with the challenge of winning events, competing for major championships, keeping your card, and qualifying for the Ryder Cup team. But what comes after? Once the calendar turns to March or April how do you evaluate whether those changes worked or whether your performance shows that you’re on the path towards improvement and meeting your goals for the year?

It’s important at that time to understand each aspect of your game in a detailed way. Obviously you’ll want to know how successful any specific changes you’ve made have been, but it’s also useful after the first two months of the season to take a look at the big picture of results. Where do I stand now compared to my peers on Tour considering my entire game?

Introducing Performance Index

To measure performance over the entire game 15th Club has developed our Performance Index – designed to measure each golfer’s underlying performance across all rounds. Think of Performance Index as a measure of your performance versus your peers that you compete alongside. Our Performance Index uses each player’s scoring average in each round, but we apply intelligence to the data by adjusting for the difficulty of the course and weather, the strength of the field, and the strength of the tour you’re competing on. Our data covers every professional tour – including the PGA Tour, European Tour, Asian Tour, Sunshine Tour, and Challenge Tour.

We can calculate Performance Index for any period of events; this gives us the ability to show how performance changes over time. We can compare the first two months of 2016 to your week-to-week performance from 2014 and 2015 or to the last six months of 2015 or to each January/February stretch of the season from the last five years. We can even look at your specific Performance Index at each course to find where you’ve had the most success or to find events where your game hasn’t fit with the course.

Performance vs. Results

Other golf rankings like the Official World Rankings (OWGR) or Race to Dubai aren’t designed to necessarily measure performance. They’re designed to measure who has accomplished the most over a given period of time. Those are able to identify the most accomplished players and use their rankings to award positions in elite events (OWGR) or to award playing privileges for the following season (Race to Dubai). However because such systems are designed to show the most accomplished golfers rather than to measure performance, certain players always have on-course performance that exceeds their rank in OWGR or Race to Dubai. In other words, the rankings are not always a good indicator of a golfer’s true underlying performance.

One major problem is how both the OWGR and Race to Dubai award by far the largest amount of points to the winner each week. Winning is obviously the goal and a huge accomplishment, but it’s often the case that the winner’s performance is only a stroke better (or tied!) with the player(s) in second place. This creates a situation where a very strong performance is not fully rewarded with the points that it would normally deserve. Performance Index avoids that problem by rewarding each player for how well they play over every hole in every round in every event.

One obvious example where players received vastly different World Ranking points for very similar performances was The Open Championship last summer. Zach Johnson (1st), Louis Oosthuizen (P2), Marc Leishman (P2), Jason Day (T4), and Jordan Spieth (T4) all finished within one stroke of each other – clearly separated from the rest of the field. Johnson, Oosthuizen, and Leishman finished with a Performance Index score of 3.65 (they beat the field adjusted for conditions by 3.65 strokes per round) and Spieth and Day finished with a Performance Index score of 3.40 (they beat the field adjusted for conditions by 3.65 strokes per round).

With the “winner take most” World Ranking system, Zach Johnson received 100 OWGR points as the winner, Leishman and Oosthuizen received 50 for losing in the playoff, and Spieth and Day received 27 for tying for 4th place. In other words, Johnson received double the points of Oosthuizen/Leishman for the same 72 hole score and four times that of Spieth/Day for winning by one stroke. This is fine for measuring accomplishment. Zach Johnson won one of the most important events of the year and should be rewarded accordingly. However, when judging performance and placing it in the context of the rest of the field and rest of the season, Zach Johnson’s play was neither twice as good as Oosthuizen or Leishman’s, nor four times better than Spieth and Day’s.

Measuring Success

One major benefit of Performance Index is that it is closely aligned with traditional measures of success like World Ranking points and prize money earned. The two graphs attached below this paragraph show the relationship between Performance Index by event and World Ranking points/Euros earned in European Tour events from 2013 to 2015.

Performance Index vs. Prize Money

There’s a clear relationship between Performance Index and World Ranking points/Euros earned, but there are certain performances – often in events with smaller purses or weaker World Ranking fields – where a golfer performs extremely well versus the field but is not compensated with prize money or ranking points accordingly. For example, in Charl Schwartzel 2012 Alfred Dunhill Championship victory, his Performance Index was 5.88 (he beat the field adjusted for conditions by 5.88 strokes per round) – one of the best of the decade as he won the tournament by 12 strokes. He won only 22 World Ranking points, but our Performance Index credits him for a massive victory – again, one of the best of the decade.

This aspect of Performance Index is ideal for measuring performance over a short period of time. Over two or three months it’s typical for a good stretch of play to not be rewarded with a victory or other high finishes. For example, our Performance Index credits Phil Mickelson with one of the two best starts to the 2016 season, but he has fallen just short of winning several times so far. However, consistently good stretches of play will be measured by 15th Club’s index – allowing a golfer to know that his game is in good shape.

Predicting Future Success

Performance Index can often serve as a leading indicator of future success. Often players establish a better level of performance before achieving the victories or high finishes that lead to a high World Rank or Race to Dubai finish. In 2014, going into the week where he won the Nedbank Golf Challenge, Danny Willett ranked only 83rd in the world, but ranked 21st best in 15th Club’s Performance Index over the 2014 season to that point. Therefore, it has been no surprise to see Danny Willett win three times in the fourteen months since and improve all the way to #14 in the world.

In fact, based on our research golfers who are ranked between 75 and 125 places better in our Performance Index versus their World Ranking at the end of a season improve their World Rank by an average of 20 positions the following season. In other words, golfers who were playing better than their World Rank indicated improved the next year. For golfers ranked between 75 and 125 places worse in our Performance Index versus their World Ranking at the end of season decline on average by 31 positions the following season.

A great example of this phenomenon is Gary Stal’s 2015 season. Stal played well in 2014 – finishing the season ranked 137th best in our Performance Index, but his OWGR rank lagged behind at 435th. Stal changed that immediately with a victory and two top 5s in the first month of the 2015 season. Stal ended 2015 48 positions higher in the Race to Dubai and 303 positions higher in the World Ranking.

Right now, for example, we have identified a pair of Americans – Harris English and Brendan Steele – and a pair of Europeans – Luke Donald and Francesco Molinari – as the players whose Performance Index predicts will rise up the World Rankings in 2016. Let’s see.