FAQ: WORLD GOLF RANKINGS

It seems like I have gotten a lot of questions lately about how my rankings work, as well as more readers interested, so here’s a basic explanation. I’ll link to it on the Rankings page as well.

Purpose:
Most golf rankings are wrong. They are wrong for several reasons. They assume tournament golf is played against a course. It is not. It is played against a field. You hear this all the time when people will say things like “Justin Rose has been under par in 9 of his last 10 rounds” while “Tiger Woods has only broken par once in the last few weeks.” The problem is, this is completely meaningless. Rose played in three tournaments where the winning score was -18, -15 and -10. Tiger played the US Open, where the winning score was EVEN par. Now, Rose played well, but even playing that well in the US Open probably would have meant 2 or 3 rounds over par.

The second big area that I see that is wrong(and this happens with a lot of rankings systems) is they are created to essentially objectify human biases. In other words, they take what is already assumed to be true by general knowledge and use a computer to fairly rate all teams/people. This is the main problem with the Official World Golf Rankings. While they assume that the majors mean more because they are majors, I ask why?

With those two problems in mind, I had the following goal when creating these golf rankings:
-Start with zero assumptions.
-Create an objective system that rates a player compared to the average PGA Tour field.

Calculating
The process is simple. Golf scores, as a measure of skill(in the long run), are normally distributed. That allows us to get a standardized score from every round. So, let’s say Tiger Woods shoots 69 in the Masters, when the field averaged 72. The standard deviation for the field is 3. Tiger’s round score would be (69-72)/3=-1. Similarly a player who shot 75 with a field average of 78 and same standard deviation would have the same score. It doesn’t really matter what you shoot, but how the field did when you shot it.

That brings up another issue, is every field the same?

The answer to that is, no. The second step is assigning a field strength to every round played. I take the standardized round score above, and add in the raw field average from the past two years. This varies widely. Something like a WGC(usually strongest fields in the world), PLAYERS or weekends at Major(Aside from PGA and lesser extent Masters, there are enough random qualifiers that get lucky to get into fields that first two rounds of majors are basically an average tour stop.*) will give around a -.25 adjustment to the field, while the first round of the Turning Stone Championship will be around +.1 to whatever the raw score is.

The final step is the tour adjustment. A player with a .00000 ranking would be playing at a level of the PGA Tour average. But, there are three tours accounted for in my rankings. Unlike the world golf rankings, which assume that the other tours are worse(and by how much) my NW and EPGA adjustments are based on comparative rounds over the past 2 years. For PGA to EPGA this generates about 6000 rounds, while its around 4000 rounds for PGA to NW. In individual cases there are varying degrees of success overall, but when you take the whole world of golf it seems these are pretty good adjustments. Obviously, as the standard the PGA Tour recieves no bonus for the Tour adjustment. However, in general players are about .2 worse on the PGA than EPGA, and .35 worse on PGA than NW. So, I add those factors to the adjusted fields above.

So, a players ranking is:

Standardized Score+Raw Field Average+Tour adjustment.

For Tiger Above it would be:

-1+(-.25)+.00=-1.25

What this says, is against a field of average PGA Tour players, Tiger would be 1.25 standard deviations better than the mean. The same 69 against a field of the Nationwide Tour players at a weak NW event might look like: -1+(.05)+.35=-.6

Using a 69 at the US Open and comparing it with a 68 at the Travelers is like comparing apples to oranges. With the above calculations, all scores are in the form of apples.

Rankings
If you’ve seen my rankings at all, you will know that there are two components. Ranking and standard deviation. The rankings are the average score of all rounds calculated like above for a two year period. The standard deviation is the standard deviation of all rounds played by a player over a two year span. Interestingly, as a rule of thumb, better players tend to be more consistent. While the average tour player has a ranking of .000 with a standard deviation of 1, Tiger is more like -1 with a standard deviation of .9.

Weighting
My rankings are not weighted to any recent performance. That’s not saying it is completely meaningless, but it’s hard to say what value it has. From what I’ve found in limited research the relative importance of recent tournaments varies widely and is only fractionally more important than random tournaments. Same applies to course form.

Calculating Odds
The rankings above represent a players score in relation to the average PGA Tour player and his consistency or standard deviation over one round. To convert it to four, just multiply by four (or three or two, etc.) The standard deviation for multiple number of rounds I found by running some simulations. For the average player(.000,1) it is around 2. I also found that these were proportional to whatever a player’s current standard deviation is. So, for four rounds, multiply the standard deviation by 2. For three, it’s around 1.7. The best way I’ve found to come up with the odds, is set a winning score and adjust it until all the sum of all players chances to win are 1. Obviously, for in-running odds, I standardize the rounds already played and proceed from there.

Planning for one big contenders/pretenders/darkhorse post as well as updated rankings on the entire field tomorrow.

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13 Comments

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13 responses to “FAQ: WORLD GOLF RANKINGS

  1. JNS

    This seems like a good way to rank golfers. The big differences I tend to see between your numbers and the odds are differences that could easily be explained by an irrational public (the odds overrating recent winners, players who played well in high-profile events, etc.). When I see Justin Rose or Phil Mickelson heavily overrated, or post-comeback Tiger underrated, I feel safe assuming that the true odds are much closer to what’s found here.

    But what leads to the differences on the extreme long shots? Surely 5dimes has no rational incentive to offer Matthew Goggin at twice the fair odds. Do they not factor in standard deviation appropriately? Do they take something into account that you don’t? Or are they just subject to the same biases the public is subject to (i.e. overweighting majors)?

  2. The long shots are interesting.

    For one, I think at some point people would start betting on the extreme longshots if the price got too high. It wouldn’t take more than a few 5 dollar bets to cost the books a lot at 5000-1. Why not just be safe and set the max at 1000-1?

    Obviously, Goggin is one guy that I’ve been high on recently probably a lot because of the standard deviation. Part of that could be because of a good 2008 and bad end of 2009-2010. In all cases, I would look at overall career performances as well as using these rankings. It’s also interesting to note that Stricker is another guy I have assumed I am high on based on standard deviation, and he is probably the most profitable “to win” bet over the past 2 years, so I’m not entirely sure what to make of it.

  3. Jake

    Have you ever looked into whether certain players had higher standard deviations (good/bad putters, drivers, etc)?

  4. No. It’s a good idea, but the data for the skill stats is simply too hard to collect right now in a way that would make it meaningful.

  5. Interesting stats here, how did you come up with the calculations and ratings? This really helps people respect the game more I think.

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  8. andy

    When does the world golf ranking system start and end.

  9. It’s a 2-year period. So it goes from Aug 16th, 2010 to Aug 16th, 2008, plus all rounds in any tournament that was played over August 16, 2008. So, if that was the third round one week I include the first two in the rankings.

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