A little over a year ago, I came up with the idea that the relationship between a player's ability to reach the Green In Regulation and her driving ability could be measured.  I wanted to generate a number where a player would rate highly if she was either poor at driving and good in GIR, or if she was good at driving and great in GIR.  I also wanted lower ratings for the opposite tendencies.  When I was first thinking about it, I couldn't come up with a reasonable formula to generate a number so I merely compared the players' rankings in the two categories - a second-rate method at best.

After some very helpful discussions this week with Tatkins and Ruthless Mike, I came up with a basic formula and tinkered around with it until the results were satisfactory.  Here then, is my newest version of Approach Factor:

GIR * (170-TD)

Before I show you the results, I should explain the theory behind the formula.  The second factor is designed to deliver a number near 100.  Total Driving numbers range from about 75 to 65 (although the poorest drivers often sink to around 60).  The usual average number for a season's worth of data is about 69 but I decided to make the constant's target 70 for simplicity's sake.  TD is subtracted from 170 because I need the factor to decrease as TD increases.  This creates an "inverse" value of TD, so to speak.

2009 Approach Factor rankings

The link above is to the spreadsheet which shows the results for all 150 players for 2009.  I've included the player's ranking in Total Driving and GIR to help show how the progression works downwards.  For example, Ai Miyazato and Angela Stanford each reached GIR at about the same rate, .716.  Since Stanford ranked second in TD and Miyazato ranked 11^th, Ai rates higher in Approach Factor.  Here are the Top 20 players along with their respective rankings in Total Driving and GIR:

Ward ranks #1 by a wide margin because she finished third in GIR despite a TD ranking of #96.  As you can see, most of the Top 20 improved their ranking between the two stats.  The first exception is Brittany Lang, who dropped from fourth in TD to fifth in GIR.  Lang is ranked highly even so because, in my opinion, maintaining a Top 5 position in GIR is a difficult task even if the player started from a Top 5 position in TD.  On down the line this stance is maintained - Miyazato and McPherson are documented above, Lorena Ochoa fell from TD #1 to GIR #8 and is ranked #28, Angela Stanford fell from TD #2 to GIR #12 and is ranked #36.  Keep in mind, though - while I'm using the players' rankings in the two stats to describe how Approach Factor is designed, the raw numbers themselves generate the AF number.  Now let's look at the Bottom 10:

You may wonder why Becky Lucidi wouldn't be last, given that she fell so far from her tenth-place TD standing.  The reason - the players below her had much worse GIR ratings (all at least .050 worse) than Becky.  It hardly matters though - whether you rank #143 or #150, your approach shots must have been very poor.

I must admit that Approach Factor doesn't actually measure how well a player executes approach shots.  It only uses two unrelated measurements to estimate how well one gets from Point A (after the tee shot) to Point B (on the green).  Tatkins is currently mining the numbers for ways of measuring that ability more directly.  On that task I wish him much luck, for I have not found any in that arena.