A few changes were made to the formula between the 2012-2013 ratings, and the just published 2011-2012 ratings. The two big ones include:
1.) Counting a missed shot as -.87 possessions as opposed to -.75. By using the value of .75, I was essentially giving the shooter all the credit for a possible offensive rebound, which of course is silly. It should be evenly split between the shooter and rebounder, hence the new value of .87.
2.) Incorporating a defensive adjustment. This was accomplished using the Defensive Rating metric, which while not perfect, does a decent job of accounting for defense. I'm working on standardizing the values with respect to positions, but until then, we can do with my current method.
That's all for now. I'm working on a few projects, including a test for how accurate HDR is as a predictor of team success. If you have any questions about where a certain player ranked, and why, feel free to hit the comments.