There is much debate about how to measure the productivity of an NBA player. There is NBA Efficiency, the Player Efficiency Rating, Win Score, Wins Produced, Plus-Minus, Adjusted Plus-Minus, and many more. One might wonder (at least I do) with all these choices, how do the sports media evaluate talent?
Consider voting for the Sixth Man of the Year (which is the award I was thinking about last night). For the 2007 award, 127 members of the sports media considered every NBA player who failed to start half their team’s contests in 2006-07. Each sports writer chose three players, with their first choice earning five points, second place earning three points, and their third choice receiving a point. When the voting points were counted, three players – Leandro Barbosa, Manu Ginobili, and Jerry Stackhouse – captured 92% of the available points.
What do these three players have in common? Each was the leading scorer off the bench for one of the three best teams in the regular season.
Aju Fenn (economist at Colorado College) and I have a paper which we presented at a conference some time ago. The paper needs to be revised and updated, but the basic story I think is pretty solid. In an examination of the voting for the NBA’s Most Valuable Player we found two factors to dominate – points scored and team winning percentage.
What this tells me is that the sports media does not consider sophisticated – or even unsophisticated – models of player performance. Sports writers tend to consider the leading scorers on the best teams. If you can score (or in the case of Steve Nash, create assists that lead to scoring) and your team wins, sports writers believe you are great. I’m pretty sure you don’t have to be an advanced statistician to know that the media is leaving out a bit of information in their evaluation of talent.
The winner in 2007 was Barbosa, who also was the leading scorer among all NBA reserves. When we turn to Wins Produced, though, we see that – for players who received any votes — Barbosa was only the seventh most productive player.
The top sixth man in terms of Wins Produced was Manu Ginobili. He finished the year with 14.1 Wins Produced, and per 48 minutes [WP48], had a mark of 0.330. Another good choice was David Lee, who produced 13.6 wins and had a WP48 of 0.378. Despite Lee’s performance, 111 out of 127 voters did not place him in the top three. With the acquisition of Zach Randolph it does look like voters will get another chance to vote for Lee next year. One suspects, though, that the Knicks will not improve enough – and Lee will certainly not score enough – for him to crack the top three in 2007-08.
Looking past Ginobili and Lee we see that the next four players on the list – Josh Childress, Corey Maggette, Jose Calderon, and Antonio McDyess – either failed to score ten points per game or failed to play for a winning team. Again, scoring and winning appear to be the keys.
Of course these four should be happy that a few sportswriters actually placed their name in the top three. Yes, more than 100 of the 127 voters completely ignored the quartet, but a few writers thought something of these four. This can not be said by Dikembe Mutombo, James Posey, Brent Barry, Anderson Varejao, and Rajon Rondo. These five players also produced more wins than Barbosa. But none averaged double figures in points, and hence none received any votes at all.
What lesson do we learn from our study of the Sixth Man award? People have spent a substantial effort developing measures of performance for basketball players. Despite a plethora of measures to consider, though, the sportswriters – who are supposed to be experts – seem to be inordinately influenced by only two factors: Points scored per game and team winning percentage. Consequently, a player like Jerry Stackhouse – who has never been a productive pro (a point I made a few days ago) – finished third in voting for this award. In fact, 80% of voters thought Stackhouse was at least one of the top three reserves in the league. That’s right, 80%.
Why the focus on scoring?
The stat I most often see discussed in baseball is batting average. It is reported during every game and I would bet it is the one stat reporters most often turn to when discussing a hitter. Despite decades of sabermetricians noting the inadequacies of batting average, other stats – like OPS – just haven’t caught on with most writers.
And I think there is a good explanation for the persistence of batting average. Most casual fans know this measure, and the casual fan makes up the majority of any sports writer’s audience. In other words, sports writers are simply responding to what the majority of their audience knows.
My sense is that basketball fans are much the same as fans of baseball. The majority are casual fans whose attention is focused on the scorers. Consequently, despite the efforts of all the people who look at basketball statistics, the sports media will continue to focus primarily on points scored per game. That is what their audience focuses upon, and consequently we can expect in the future points per game and winning will still be the primary factors sports writers consider in making player evaluations.