Instead of going year by year, I just looked at rebounding and shot location distribution from 2006-2012. Based on my original chart, as well as the Sloan paper, I determined what the XORP (Expected Offensive Rebounding Percentage) was for each of the five major shot locations (Hoopdata).
At Rim - 40%
3-9 feet- 25%
10-15 feet-25%
16-23 feet- 15 %
16-100 feet- 30%
These are approximates for now. When I move onto Defensive Rebounding, I will test the weights again, but these numbers worked well for Offensive Rebounding.
The rest was simple. I totaled every team miss based on shot location, ran them through the XORP, and then compared them to the number of Offensive Rebounds they actually collected.
There was a 17.6% Correlation between XOR and actual Offensive Rebounds.
I then subtracted XOR from the Actual, to get each teams rebounding difference (XORD). This would ideally be a better measure of rebounding prowess then traditional rebound totals, as it attempts to remove the impact of shot locations from the equation. I decided to test this, by regressing both Actual Offensive Rebounds, and XORD, against team winning percentage from 2006-2012.
Actual Offensive Rebounds had a -4.5% correlation to winning. Yikes. This would indicate collecting traditional offensive rebounds tends to be the province of bad teams.
XORD (Expected Offensive Rebound Difference), had a -.006% correlation to winning. Not an ideal value, but approximately 750 times better at leading to wins then traditional offensive rebound metrics.
The results are mixed, but encouraging overall. Shot locations play a significant, but not huge role in rebounding totals. The difference between the XOR and the actual rebounding numbers, is the XORD, which is a much better rebounding metric then traditional offensive rebound totals. It attempts to take out the impact of shot locations, and has a much higher correlation to winning.
That's all for now. Comments and suggestions are welcomed as always. I'll run the study for Defensive Rebounding, and see what turns up. If you are curious to see which teams had the highest XORD, I'll be posting some tables under a separate tab on the menu.
*Spoiler Alert*
In 2011 and 2012 the Miami Heat went to the NBA Finals. In 2011 and 2012, the Miami Heat were ranked #1 and #2 in XORD. Guess they can rebound.
In 2007 the Spurs were ranked 26th in XORD. In 2007, the Spurs didn't care, and won the title anyway