Revisiting Dean Oliver

It’s been a couple of years since I’ve recorded basketball stats on this site using Dean Oliver’s methodology, so I guess it’s time for a quick primer on his methodology.

What Oliver does with his individual ratings is ultimately not that different from the stats I currently track using John Hollinger’s method.  I respect the work of both of them tremendously, so if you haven’t had the chance (and are interested in this sort of thing), you should read Oliver’s Basketball on Paper and Hollinger’s yearly Pro Basketball Forecast.  They both write very well, with some humorous analysis thrown into the detailed stats.

Team Offensive and Defensive Rating

Like Hollinger, who calls his rating of a team’s performance per possession “efficiency,” Oliver tracks offensive and defensive “rating.”  They’re essentially the same concept, but Oliver’s estimates of possessions are a bit closer to reality.  Hollinger’s formula tends to overestimate them, resulting in lower numbers for efficiency.

Individual Offensive Ratings

Oliver extends his Offensive Rating concept to the individual, with a complex formula that determines the value of an assist within a game context and then assigns weights to offensive events from the box score to determine a player’s individual number of total possessions, scoring possessions, and points produced.  From these, we can get what he calls “floor percentage” (scoring possessions/total possessions) and Offensive Rating ([points produced/total possessions]*100).

Individual Defensive Ratings

Defensive Rating is a similarly complicated concept using Oliver’s methods.  However, there’s a problem with implementing it: most of the stats needed don’t exist in traditional box scores.  In order to get a good gauge of a player’s defensive value, we need stats that correspond to important offensive numbers, like field goals attempted and made (or defensed).  In reality, we only have defensive rebounds, blocks and steals, and from those numbers Oliver estimates a number of “stops” created by each player and estimates possessions faced by the number of minutes played.

Because of limited data, these estimates are quite rough.  For instance, we know that certain defenders are always assigned to superior offensive players (Trent Morgan comes to mind).  Others play statistically more valuable defensive positions, like center (and arguably point guard).  Still others make their livings as defensive “lurkers” who don’t play well on the ball but rack up cheap steals, blocks, and rebounds.  For this reason, I don’t place a lot of weight on the defensive rating (and consequently, the net rating).

Conclusions

I think Oliver’s stats will add more to the stats I currently present, or I wouldn’t track them.  It’s interesting to see where differences pop up, and I’m sure I’ll examine some of those as the season progresses.  For now, check out the new stat file here, updated through 12/10.

The Bisons have their final home game before the new year tonight against Drury (MO).  I don’t know if it will be broadcast online, but you should check it out If you’re not out partying to celebrate Christmas, the end of the work week, or my birthday eve’s eve.

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