By definition, PGA Tour professionals play the highest standard of golf. But for the longest time, it hasn’t been clear what about their game mattered most.

Now, based on the tour’s expansion of the revolutionary strokes-gained concept that officially began at the Memorial Tournament, we will know much more.

When the tour first began compiling statistical-performance categories in 1980, we learned some basics: how far the pros hit their drives, how often they hit it in the fairway, how often they hit the green in regulation. But the stats were limited and, in many cases, flawed when it came to determining quality of performance.

What the tour didn’t have was a clean way to accurately portray a player in terms of his advantages and disadvantages relative to his peers. Arguments about who was best at a particular area of the game were largely matters of opinion.

In 2004, the tour began to use ShotLink, which through laser technology measures (at most tour events) the distance every shot is hit and its resulting distance to the hole. Through ShotLink, which the tour continues to develop with the help of CDW, officials were able to establish a baseline probability for players holing out from every distance, using historic data and tour averages, so that every putt taken could be calculated as having gained or lost an advantage against the field.

Thus was born, in 2011, strokes gained/putting, the first implementation of the revolutionary concept. A simple example of how it works: Because the probability of making an eight-foot putt has been determined as statistically 50-50, making the putt would give a player a plus-.5 stroke gained. Missing it would be a minus-.5 stroke gained. After every putt in a round is calculated, a strokes-gained figure goes into the books. Through strokes gained/putting, we have learned who truly are the best putters.

But putting, as ShotLink taught us, statistically makes up only 15 percent of the best player’s scoring advantage. So in 2011, the tour began working on extending the strokes-gained concept to the other 85 percent of the shots. By accumulating collected data (some 5.2 million shots), the tour created a baseline average for player performance from all distances and locations (fairway, rough, sand, recovery) so that every shot not on the green is accorded a statistical expectation for the number of strokes required to hole out.

Based on ShotLink data, some samples of scoring probability: 519 yards, 4.5 strokes; 410 yards, four strokes; 168 yards from the fairway, three strokes. More stroke probabilities: 100 yards from the rough, three strokes (the same probable score from sand from 54 yards); 30 yards from the fairway, 2.5 strokes; seven yards from the fairway, two strokes.

Strokes gained for shots not on the green are determined thusly: When a player improves his expected score on the hole with the shot, he gains some variation of a fraction of a stroke over the field. When he worsens his expected score with the shot, he loses a fraction.

Last week, the tour announced it has new categories for shots from off the green: strokes gained/off the tee (tee shots on par-4 and par-5 holes), which among the top-40 players is 28 percent of their scoring advantage; strokes gained/approach to the green (tee shots on par 3s and second shots on par 4s and par 5s), providing 40 percent of scoring advantage; and strokes gained/around the green (shots from within 30 yards of the edge of the green), which are 17 percent of the scoring advantage.

There were some enlightening findings.

In off-the-tee category, so far in the 2015-’16 season, Rory McIlroy has been the best, followed by Bubba Watson and Dustin Johnson. In a surprise, Jordan Spieth—he of a recent spate of one-handed follow-throughs, but apparently manageable misses—is a very respectable ninth. Meanwhile, over the past six years, Watson has been the best driver on tour, by a lot. He is the only player to have an average gain of more than one stroke a round in driving.

Approaches are the area where players can produce the biggest strokes-gained advantages, because as Mark Broadie, the Columbia University professor who conceived the strokes-gained concept, says, “There are a lot of these shots, and the skill differences are wider.” This year’s leader is Adam Scott, by nearly two strokes. It turns out that Spieth has struggled in iron play more than any other area, ranking 106th, which gives some perspective to his fateful 9-iron on the 12th hole at this year’s Masters. Over the past six years, Jim Furyk has been the best iron player. This was also the area in which Tiger Woods established his biggest advantage over the competition. He retroactively led the category in 2006, 2007, 2009 (after an injury-interrupted 2008), 2012 and 2013.

Around the green, Spieth is the leader, with Patrick Reed second. McIlroy is a better-than-expected eighth, and Dustin Johnson’s rank of 134th points to his ongoing weakness with short shots. Over the past six years, Luke Donald has been the best, with Kevin Na second. Presumed short-game wizard Phil Mickelson has cracked the top 10 only once in the past six years, and only twice in the past 10. Lefty did achieve the highest around-the-green stroke savings ever recorded in a tournament—14.948 shots—at the 2007 Deutsche Bank, where he had four hole-outs and was seven-for-seven from bunkers in winning by two shots.

In putting, World No. 1 Jason Day is leading (picking up better than a stroke a round on the field), which would indicate that when it comes to winning, putting is usually more than 15 percent of the victor’s scoring advantage. Spieth, widely considered the best putter in the game, ranks sixth. In the past four years, Aaron Baddeley has been first, gaining 2.866 strokes per tournament, and he is the only one in the top 10 each of the past four years.

In expanding the power of strokes gained, the tour has brought more fact-based understanding to a complex game. And the more that’s known—well beyond a hole’s par—about what it takes shot by shot at the highest level to gain or lose ground, the more interesting the game becomes.

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