Tyler Cowen’s The marginal product of NBA players points to a Washington Times article on how Wayne Winston, professor of decision sciences at Indiana University, has tried to apply Moneyball style statistics to basketball — starting with a popular hockey statistic:
Winston ran the concept by Sagarin, a close friend since their days as fellow MIT undergraduate math majors. They settled on a variation of hockey’s plus-minus system, in which players are judged by how well their team plays while they are in the game.In the NHL, for instance, a player who is on the ice when his team tallies a goal earns a rating of +1; if the team yields a score, that same player would receive a -1 mark.
“Basketball’s a team sport, and lots of things aren’t tracked,” Winston says. “Like taking the charge, going through a screen, tipping a ball to your teammate, saving a ball from going out of bounds. That’s where our system comes in. All these little things should translate into points.”
It takes a bit more analysis than that though:
One problem: Traditional plus-minus systems tend to overrate average players on good teams and underrate good players on lousy ones. After all, a zero plus-minus rating on the Los Angeles Lakers is not the same as a zero rating on the Los Angeles Clippers, mostly because one team has Kobe Bryant and Shaquille O’Neal and the other has Marko Jaric and Chris Kaman.To compensate, Winval’s ratings are weighted to take into account every other player on the floor. For every time segment a player is in a game, the system tracks the other nine players on the floor, the length of the segment and the score at the start and end of the segment.
Naturally, the results don’t match popular wisdom, as Tyler Cowen points out:
Please sit down, the five best players in the NBA, according to this measure are:1. Hedo Turkoglu (who? he plays for San Antonio but doesn’t even start)
2. Vince Carter (a well-known star, but universally considered soft and a choker)
3. Kevin Garnett (the likely MVP for this year)
4. Brad Miller (very good player, but not elite)
5. Manu Ginobili (very good player, perhaps headed toward elite status)Shaq, Kobe, and Tim Duncan are not in the top ten. None of the five, except for Garnett, crack a recent USA Today straw poll for NBA mvp.