Is Groove Rule Finally having an Effect?

As we all wait for the weekend and whether Sweden's test of a shorter golf ball will either fuel or douse the flickering flame of a ball rollback, I am reminded of the last golf equipment standards speculation kerfuffle of this generation: the grooves debate.

The grooves debate, which led to the rule change that was designed to reduce the effectiveness of grooves to impart spin to the ball for shots out of the rough (among other things), got its public start when USGA Senior Technical Director Dick Rugge studied the correlation between various golf statistical skills (driving distance, putting, greens in regulation, driving accuracy) and rank on the money list. Rugge produced some charts based on that research that showed most notably how the correlation coefficient between driving accuracy and money rank had deteriorated to the point where it was less than zero by 2004. Throughout the 1980s and early 1990s, it was around 0.5, which is a pretty significant correlation as these things go. (For you non-statistics geeks, a correlation coefficient ranges from 1 to -1. Example: A correlation of "1" means the player ranked first in driving accuracy also was ranked first on the money list, and so on down the line. A correlation of -1 means the person ranked last in driving accuracy is ranked first on the money list. A correlation of "0" means there's no statistical link between driving accuracy and money rank.)

The groove rule eventually developed from there, and since its implementation on the PGA Tour in the 2010, the question has been would the correlation between driving accuracy and money rank return to the halcyon days of the 1980s. Rugge has made the case that it would take three years before anyone should start seeing how the rule might be changing play at the elite level.

We're six months away from the three-year mark, and while there has been little indication in the first two years that the correlation between driving accuracy and money rank has changed, there is a curious movement in the numbers this year.

By my calculations, through the first five months the correlation coefficient is 0.38. If maintained through the end of the year, it would be the highest that number has been in 20 years. For the last three years that number, by my figuring, has hovered around 0 (again meaning there is no relationship between a year of driving accurately and a year of consistently winning a lot of money). It's about five times the average of what it was from 2001 to 2006.

Could the change in grooves be dictating who is successful on tour? So far this year 13 of the wins have come from players who rank in the top 50 in driving accuracy. Only 4 winners this year rank outside the top 100.

Half a year does not a trend make, but it bears watching.

--Mike StachuraFollow me on Twitter @MikeStachura