Q&A with the godfather of golf analytics

This Q&A with Mark Broadie originally ran July 22, 2015. Broadie invented the strokes gained method of measuring golf performance. The PGA TOUR released three new strokes gained statistics on June 1, 2016: strokes gained: off-the-tee, strokes gained: approach-the-green and strokes gained: around-the-green. Along with strokes gained: putting, Broadie's method of measurement can now be used to analyze every aspect of a player's game.

Mark Broadie is the godfather of advanced golf analytics. He developed the “strokes gained” system that is behind the widely used strokes gained: putting and strokes gained: tee-to-green statistics.

Broadie’s system is a better way of isolating and analyzing individual aspects of a player’s game. Old golf statistics, such as greens in regulation and putts per green, are dependent on other shots. For example, greens in regulation is influenced by a player’s driving because a player who misses a lot of fairways may be blocked by trees from hitting the green with his approach shot. Players who hit their approach shots closer to the hole may have fewer putts per green in regulation than a player who is a superior putter but doesn’t hit his approach shots as close.

Broadie is the Carson Family Professor of Business at Columbia Business School. He has a PhD in operations research from Stanford. His book, “Every Shot Counts,” was released last year. It is an in-depth look at his quantitative research in golf. He spoke with PGATOUR.COM about what he has learned in more than a decade of collecting and analyzing golf data.

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PGATOUR.COM: How did you become interested in bringing quantitative analysis to golf?

BROADIE: I probably started thinking about (strokes gained) in 2000. A long time ago, I started trying to understand the amateur game and why different amateurs score differently. Where did the 10 strokes come from that separated a 90-shooter from an 80-shooter? That required data. I created a program to capture data on amateurs’ shots around the same time the PGA TOUR came up with ShotLink. My system, called Golfmetrics, was almost like a personal ShotLink system except a lot more painful because you didn’t have 300 people capturing the data for you.

I spent years gathering data of amateur players from 7 years old to 70 years old. We collected more than 100,000 shots in the data. It’s a large sample, but small compared to what has been collected with the ShotLink system.

PGATOUR.COM: What was the most surprising finding in your work?

BROADIE: The most surprising finding to most people was the number of strokes gained by putting versus other parts of the game. Putting turned out to be about 15 percent of the shots between better players and average players, and that was the surprise, that it was so small. The biggest difference is in ballstriking, especially the number of severely-penalized shots that high-handicappers hit (i.e. hitting a shot out of bounds).

PGATOUR.COM: What’s next for “strokes gained?”

BROADIE: The PGA TOUR is working on splitting strokes gained: tee-to-green into strokes gained: around-the-green, strokes gained: approaches and strokes gained: off-the-tee, to give a little bit more detail about different shots between the tee and green.

PGATOUR.COM: Give an example of where strokes gained provides superior analysis than traditional statistics.

BROADIE: The advantage of strokes gained: putting over other stats shows in Dustin Johnson’s play this season. Through the John Deere Classic, he is ranked very high in putts per round and putts per green in regulation and very low in strokes gained: putting. He is second in putting average (putts per GIR) and 13th in putts per round and, in strokes gained: putting, he’s ranked 125th. Those are huge differences. One says he looks like the best putter on TOUR and one says he is below average, and which would you believe? I think most people who have seen Dustin Johnson play would believe the strokes gained: putting over the other statistics.

There’s a simple reason for that. He’s such a good ball-striker, and has such a good short game, that his putts start way closer to the hole than an average TOUR player, so he takes fewer putts and he takes fewer putts per greens in regulation not because he’s a better putter but because he’s starting closer to the hole. Strokes gained: putting takes it into account that if you’re starting from 10 feet versus 15 feet, you’re on average going to take fewer putts. So when you adjust or control for the initial distance of the putt, it’s a much more accurate reflection of the skill, which shows that he is a slightly below-average putter.

PGATOUR.COM: Why is ball-striking so important?

BROADIE: One of the things the ShotLink data and this way of analysis clearly shows, is that the long game is the separator between the best TOUR pros and average TOUR pros. … The long game explains about two-thirds of the scoring differences and the short game and putting about one-third. This is true for amateurs as well as pros.

Rory McIlroy is Rory McIlroy because in his career, he’s ranked first in strokes gained: driving (gaining an average of one strokes per round) and he’s ranked seventh in stroked gained from approach shots (gaining 0.7 strokes per round). Those two categories account for 1.7 of the 1.9 total strokes per round that he gains on the field. Short game and putting only contribute an average of 0.2 strokes per round to his total gain. It’s really his ball-striking that accounts for his success.

Ball-striking separates, in terms of strokes, the better players from the average players more than other parts of the game. There’s more of a difference in skill there. I think part of the reason is that if you look at proximity to the hole, and you ask, how much difference does it make to be 27 feet versus 30 feet, it sounds like it makes no difference. You’re probably going to two-putt from 27 feet, you’re going to two-putt from 30 feet, it doesn’t seem that it matters. But it’s not the 27 feet to 30 feet on the green that matters. It’s the shot in the bunker that is in the fringe instead, or the shot that lands on the green instead of the rough, or the 10-footer that becomes a 7-footer, or the 5-footer that becomes a 2-footer. You add up all that and it is a large difference.

PGATOUR.COM: When did a TOUR-level player or instructor first approach you?

BROADIE: Pat Goss was the first one with Luke Donald around January 2010, and then Edoardo Molinari from the European Tour. Then there was Sean Foley and a bunch of others. If you add up the number of coaches or players who have called for some sort of information, it’s 40 maybe.  More coaches than players have contacted me, but Edoardo Molinari was a little bit of an exception. He implemented strokes gained on his own, because the European Tour doesn’t have ShotLink data, so he changed his own shot-recording system that he developed to compute strokes gained stats, and he’s done that for years. He has a master’s degree in financial engineering, so we have similar backgrounds.  I’d say they’re not all on a regular basis, but a bunch have called me.

PGATOUR.COM: What do players use strokes gained for?

BROADIE: It’s mostly for looking at more detailed analysis of where their strengths and weaknesses are. There is occasionally a question about how aggressive or conservative to be on a certain hole, like the 10th hole at Riviera, but that’s not the majority of what players are asking.

PGATOUR.COM: How do players implement strokes gained in their practice?

BROADIE: I think everyone is looking for an edge. On the PGA TOUR, you may know that you’re good in one area and maybe not quite as good in another area, but to convert that into, ‘Well, I’m 6/10 of a stroke better than the field on this type of a shot and I’m losing 2/10 of a shot on this other type of shot,’ is really hard because you’re looking at really small gains and losses. It’s not a surprise for some players, but others don’t realize they may be good at a certain part of the game or that there’s room for improvement in another area.

PGATOUR.COM: Did collection of data impact your play or practice at all?

BROADIE: It helped in a number of ways. One, on certain holes I ended up using a different club from the tee because I could see what my shot pattern looked like. That’s just one thing that can come from looking at the data. Then, in analyzing risk and reward, on certain holes I was taking too much risk when there was, say, out-of-bounds on one side of the hole. It helped in a number of places.

Putting together a monthly strokes gained report has helped me. I remember the reports showing me that my short game was slowly deteriorating. It’s very easy as a golfer to remember your best shots and think, ‘I’m doing well because I remember this great shot I had,’ but when you have this somewhat slow deterioration, and then you get a report saying you’re losing two more shots per round in your short game than you were two months ago, then you realize you should practice it. It’s much easier to focus your practice time when you have this measure telling you where you’re doing well or where you’re not doing well.

PGATOUR.COM: Was there anything in your previous academic career that helped you formulate this or played a part in your study of golf?

BROADIE: Absolutely. There’s a couple major connections. One is the mathematical technique of simulation. One way you can analyze, say, a strategy of hitting driver versus 3-wood, or using a different target off the tee, is that you use the computer to simulate a lot of shots. Once you have this database of shots  in the computer, you can play the hole 1,000 times using one strategy and 1,000 times using another, and see which is better. That simulation technique is used a lot in finance, operations, and in many other areas of business. That’s part of my background that I could apply directly to golf analytics. The other part is this area of optimization, where determining the best strategy on the tee depends on the next shot and the next shot. Your target off the tee depends on where the hole is and so the way you figure out the strategy on the first shot shot is you have to start from the green and work backwards. In the mathematical world, that’s called dynamic programming. You’re trying to optimize a sequence of decisions over time. That also happens a lot in finance applications and business applications.

PGATOUR.COM: How much do you get to play?

BROADIE: I was playing more before writing this book. I was probably playing a couple times a week, and then it went down to once every other month. I play at Pelham Country Club in Westchester, New York. I’m hoping to get back to playing once a week.