My last post focused on media’s decision to give the 2009 Rookie of the Year award to Derrick Rose.  The post began by noting that Rose was essentially an average point guard in 2008-09.  It then proceeded to offer the following argument:

So why was he named Rookie of the Year? 

The key issue is point score per game.  Rose had the second highest scoring average among rookies. And since the leading scorer – O.J. Mayo – played on a losing team (and was also drafted after Rose), we should not be surprised that most of the media focused on the point guard from Chicago.

Explaining the Vote

After writing this sentence I thought it might be a good idea to investigate my claim.  Essentially I am arguing that the media primarily focuses on scoring in voting for the Rookie of the Year.  And beyond scoring, draft position and playing for a winner also matters.

My argument is bolstered by past studies – detailed in The Wages of Wins and elsewhere — of how talent is evaluated in the NBA. However, none of these past studies – at least, none that I am aware of – looked specifically at voting for the Rookie of the Year.  So I thought I would spend a bit of time seeing if the conjecture I offered was supported by some empirical evidence.

The study begins with the voting process.  The Rookie of the Year award is decided as follows: Each member of the sports media asked to vote for this award names three rookies. The top choice from this trio receives five voting points.  Second place is worth three points.  And the third choice receives a single point. After all the votes are in, the voting points of each rookie placed on a ballot are added together.  The rookie with the most votes gets a trophy.  And everyone else gets to wonder why they didn’t get a trophy.

With voting explained, we now need to look at the data.  As is the case with all awards given out by the NBA, voting data for the Rookie of the Year can be found at Patricia’s Various Basketball Stuff, a great NBA website maintained by Patricia Bender. According to Patricia’s website, from 2003 to 2009, 62 rookies received at least some consideration for this award (prior to 2003, Patricia Bender only reports the players who received a first place vote). What we wish to identify is the factors that caused the voting pattern we are observing.

Let’s start with a very simple model.  Specifically, let’s regress voting points on the three variables identified earlier:  points scored per game, team wins, and draft position.  To this list I am going to add two more factors: number of games played and the size of the market where a rookie plays his home games. Continue reading →