The Numbers Game: Reader Email, Volume One

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By Dave Koster via TheSandTrap.com

A couple of readers chimed in on the 40-30-20-10 rule and had some interesting thoughts. In answering them, it helps explain, define and prove why I set it up the way I did.

A popular sports radio host says "if you take the time to email me, I'll take the time to read it." The same goes for me. Of course, he probably gets tens of thousands more emails than me. Still, I do read and think about the emails I receive, and I encourage you to send me more. Our email addresses can be found on the staff page.



Over the past few weeks, two emails in particular have inquired about The 40-30-20-10 Rule. Recently, I applied the rule to the LPGA and to the Champions Tour. Both emails posed questions or suggestions that I thought I'd answer here.

Email Number One: Will

I took a look at your spreadsheet, and experimented with the data. I think there's a problem. I can illustrate it by changing your rule to 10-30-20-40, exchanging GIR and DA. If you plot those results, you get a similar correlation. In fact, you will get similar correlations with any percentages you choose.

Your idea likely has merit, but you aren't applying the data in a meaningful way. I will experiment a bit more tonight, and see if there's a better method.

It's an interesting thought. I ran through an assortment of variations of the 40-30-20-10 rule and shifted weight in different directions. Ultimately, what led me to the way the rule is weighted now is the research I did on the correlation of each statistic to scoring and earnings. No matter the tour or year, it always fell in this order of correlation, strongest on the top and weakest on the bottom:

1. Greens in Regulation (GIR)
2. Putting
3. Driving Distance (DD)
4. Driving Accuracy (DA)
   

Probably the only exception to the general rule is DA, which has gone from strong to weak in correlation over the past 20 years or so. Still, we are talking about the game as it is today… and today it is greens and putting.



To better represent (and validate) the research I've done, I wanted to show Will and everyone the difference between what Will suggested and the 40-30-20-10 rule as it is today. Since I had the Champions Tour data handy from last week, I thought that I'd just flop the GIR and DA and plot the same graphs.



Here's Will's graph:







And here is the graph from last week:







I can see why Will and others would think that the first graph is not that much different than the normal 40-30-20-10 rule graph. The slope of the graph is similar, but the difference is in the proximity of the points to the line. This is represented in the RSquare value to which I've previously referred. The RSquare value is a measure of how tightly a line fits the points, or a statistical term which tells you how good one set of data can predict the other. An RSquare value of 1.0 means that you can perfectly predict the outcome of one value using the other.



For Will's graph, the RSquare value is 0.6057. This really isn't too bad, but using the normal 40-30-20-10 rule, the RSquare value jumps to over 0.85, a significant increase. The slope of the line may give us a trend, but the definitive proof for which equation better correlates the data is in the RSquare value… and in the end, when GIR is 40% and DA is 10%, the correlation is much stronger.



Email Number Two: Jay

Haven't you just discovered that scoring average is the most important statistic? If you multiply GIR * Putting Average you basically get a player's score - which correlates very well with money. I understand that missed greens aren't included but when you add in total putts, that gives you a pretty good proxy for up and downs.

In fact, the more greens hit the closer the approximation to scoring average your 40 and 30 percenters get.

As Bobby Jones once said - golf is turning 3 into 2. The best way to do that is a GIR and birdie putt (i.e. lower putting average).

Of course scoring average is the most important statistic. If you hit the most greens, had the best putting average, and hit the ball great off the tee but didn't score well, you wouldn't make very much money in professional golf. The point to the 40-30-20-10 rule is to predict scoring average and earnings by virtue of the different facets of the game. Just correlating score to earnings wouldn't have much meaning to me or anyone else.



I'm a bit lost when Jay talks about multiplying GIR * PA to get a player's score. Let's take Phil Mickelson:



70.7 * 1.703 = 120.4



That's not very close to Phil's scoring average, and variations of that ((0.707 * 18) * 1.703, etc) fail to come close as well. I even tried using the rankings for each stat (40% of GIR, 15% of PA and 15% of PPR), but that too failed. I asked Jay to shed some light on this and he replied with this:

Say I hit 100% of GIR and my putting average per GIR was 1.66 that would mean that I birdied 33% of the holes I played or said another way I had (.66 * 18 = 12) pars and (.33 * 18 = 6) birdies. You have just computed my score: 66 on a par 72 course.

Now, we don't usually hit 100% GIR. On the other holes, total putts taken is pretty good proxy for how often I got up and down that day (ie saved par). For instance, total putts under 30 might correlate with a scrambling percentage of 70%. Scrambling percentage can be used to calculate your score on the greens you missed.

For the most part, this is true. The only caveat is when players get up and down for a bogey or worse after a penalty shot. I'm still intrigued by using some sort of formula to get to score by using total putts as, as Jay says, a proxy for the greens not hit. The hope would be that the 'worse than bogey' scores would smooth out over all players.



I do agree with Jay on one thing, and that's his quote from Bobby Jones. I had never heard it before and found that the exact quote is "The secret of golf is turning three shots into two." Golf is about hitting your spots… or greens, and then taking advantage when you do it. I've been in a funk lately and am having a tough time making birdie putts. I'm hitting my normal amount of greens, but my putting average is up to nearly 1.9. That means I'm only making one or two birdies per round.



This quote is even the title of a book written by Bill Moretti on the short game. While Moretti focuses on the short game, which is very important, remember that you probably won't make a two without getting on or near the green.



Thanks Guys
I appreciate both Will and Jay's input. I'm hoping to hear back from them and from others about ideas and questions on not only the 40-30-20-10 rule but other number-related topics as well. I'm going to try and make this a regular drop-in column when some interesting thoughts come up from our readers. Don't be shy and drop me an email, especially if you disagree.

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