As we saw in the Introduction, in the early part of his golf career Dave Pelz had a typically traditional attitude towards playing and teaching golf. Like most of us, he assumed that graceful textbook swings would result in lower scores. So like most golf instructors he assumed that the way to teach golf was to teach graceful textbook swings. Results would follow technique — or so the theory goes.

As Pelz describes it in his book, this assumption was given a major jolt the day he watched Gay Brewer soundly beat another golfer who had a much prettier looking swing. This eventually led him to formulate a completely different attitude towards improving one’s golf game — a more “scientific” attitude.

The first thing Pelz questioned was the assumption that perfecting one’s swing technique will have the most significant impact on one’s scores. He was not questioning the importance of technique or consistency. Rather, he was addressing the question “What makes the biggest difference to a golfer’s score?” Or to put it another way,  “How can a golfer improve his or her scoring performance?”

In the place of the normal preoccupation with swing technique came an almost complete focus on results. He stopped looking at the swing and started looking at where the balls were landing. And we’re not just talking about a relatively superficial interest in things like “fairways hit”, or “greens in regulation”.

He went far beyond simple stuff like that. Dave Pelz the scientist formulated a concept he called PEI — Percentage Error Index — and for three years he tracked and recorded and analyzed the actual shots of a large number of touring pros. This was the data he would eventually use to draw his most important conclusions.

PEI — Percentage Error Index

The PEI concept is deceptively simple. Every week at some PGA tour event Dave Pelz — the “big fat guy” with the clip board — would follow a particular group of pros around charting their shots. For each shot he would make a calculated guess as to precisely where it was supposed to land. Then he would run up to where the ball had landed and note how far from the intended target point it had actually landed.

For instance, on a 150 yard shot if the ball landed 10 yards from the target point that was a 6.7% error. The PEI was calculated by dividing the distance from the intended target — the amount of “error” — by the total distance the shot was supposed to travel — in this case, 150 yards. This gave Pelz an objective measure of a golfer’s accuracy with every club.

Pelz’s objective was to watch a player hit every club at least a few hundred times. He discovered that analyzing shots this way revealed surprisingly consistent results for every player he followed. As he says, “When I compute an average from more than 1,000 shots, I consider the PEI an absolute indication of the player’s skill with that club.” (14). In other words, if he watched enough shots he could arrive at an objective evaluation — a PEI — of a player’s skill with every club in his bag — from driver to putter.

He kept this up for about three years, creating a personal database unlike any that had ever been compiled before.

What Did the Data Tell Him?

Eventually Pelz started to arrive at some conclusions from all this data. Here are some of his more significant observations:

1. For any given player from driver down to 9 iron the PEI for all clubs was the same within about 1%. In other words a player who had a 7% PEI with his driver was very likely to have a very similar PEI with all his clubs down to and including his 9 iron. This is what he calls the full swing PEI.

2. Every player studied had a significantly higher PEI with the wedges as opposed to driver – 9 iron. The difference ranged from twice to four times as high. In other words, every player studied was less accurate with their wedges. This is what he calls the finesse swing PEI.

3. When correlated against winnings there was no correlation at all between full swing PEI and money won. (p.22) Tour players are all such consistently good strikers of the ball (all within 5.5% and 9.5% PEI) that you simply cannot say “This guy wins more because he hits better full shots.”

4. There was only a weak correlation between putting PEI and money winnings. “…the best putters were not the highest money winners.”(p.23)

5. There was a strong correlation between short game PEI and money winnings. “Up and down, all along the money list, there was a strong and meaningful correlation between how well players hit their short-game shots and how much money they won on Tour.” (p.23)

Taking the Data One Step Further

One obvious conclusion from all of this is that the importance of the short game is generally underestimated. Pelz’s data clearly showed that the most significant contributor to winning was how accurate a golfer was with his wedges. It was more important than the length of his drives or the accuracy of his irons. And it was even more important than how well he putted. Of course, Pelz was aware that the ratios that held for touring pros might not hold for amateurs.

Ever the good scientist, Pelz dug deeper into his data to try to explain this. Fortunately when he was following all those players around with his clipboard he was not only measuring how far their shots were missing their targets, but also where in relation to the target all those shots were landing. His data told him for every shot whether it was long or short, left or right.

When he charted this information he found a very interesting correlation. Players almost always missed with their full swings left or right. Their distances were amazingly consistent. A 5 iron that missed by 10 yards normally missed either left or right.

But when it came to the “finesse swing” — the wedge shots — the misses were usually long or short. In other words most players were able to hit their wedges quite straight. But they were not able to control the distance as accurately as with their full swings.

Why is This Important?

In his mountain of data Pelz had what he needed to explain why accuracy with the wedges is so important. It boils down to this: the closer a player can put his ball to the hole, the greater chance he has of making the putt. For the pros, if they could get it within six feet they had a 50% chance of making the putt. And the easiest way to get it closer is by learning how to hit your wedges more accurately.

In other words, of all the things a golfer can do to improve his or her game — at least a golfer with the consistency of a touring pro — learning how to hit the wedges closer to the hole will have the greatest impact on the score. As he says, “If you want to score, the most important ‘game’ to improve is your short game.” (31)

According to Pelz the problem of controlling wedge distances had never been addressed in a systematic way. He was going to change that. It became his mission in life to give golfers a “system” that would allow them to consistently hit their wedges predictable distances.


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