Bucks Diary

Tuesday, December 18, 2007

Explanation for my switch

Did anyone find it odd that for about a year and a half I was vigorously advocating the use of the NBA's Eff48 statistic and then all of a sudden one day I dumped it and started using this Win Score statistic instead? It was a bit of a seachange, and I really never explained why. If you care, here it is.

First, while I still find the Eff48 stat superior to traditional performance measurements like scoring and rebounding averages, it has some annoying flaws. For one, it doesn't correlate well with winning. Doing my Eff48 Boxscore, I found numerous examples where the Bucks had the superior efficiency average in a particular game and still lost. That bothered me.

Second, I always knew intuitively that counting every positive statistic on a basketball score sheet as exactly equal was a bit of dirty math. I didn't know which statistics were more important or deserved greater weight, but I knew they probably weren't all equally important to victory.

Finally, I always noticed that Eff48 overvalued "gunning". And that was the very reason I stopped sighting traditional scoring averages, so that also bothered me.

The solution to all those Festivus grievences came in a book that I've been mentioning in my last several posts, The Wages of Wins. Their research corrected all of the errors of Eff48. And though it took a while to rid myself of some of my long held but mistaken beliefs (such as my propensity to overvalue assists), I eventually accepted their work and adopted the "Win Score" calculation as my chief method of evaluation.

Here's how Malcolm Gladwell explains the same thing:

What they (The Wages of Wins authors) tell us is that the people charged with evaluating and rewarding ability and performance in the NBA do a lousy job. In particular, they argue, traditional talent evaluation over-rates the importance of points scored, and under-rates the importance of turnovers, rebounds and scoring percentage. Wages of Wins also obliterates the so-called NBA Efficiency rating, which is the official algorithm used by the league and many basketball experts to rank the statistical performance of players. The Efficiency rating, they argue, makes the same error. It dramatically over-rewards players who take lots and lots of shots.”

And here's how he explains the advantage of their Win Score and Wins Produced statistics:

“Okay: part two. Is the Wages of Wins algorithm (Win Score) an improvement over the things like the NBA Efficiency system? To make the case for their system, the authors “fit” their algorithm to the real world. For the 2003-04 season, they add up the number of wins predicted by their algorithm for every player on every team, and compare that number to the team’s actual win total. Their average error? 1.67 wins. In other words, if you give them the statistics for every player on a given team, they can tell you how many wins that team got that season, with a margin of error under two wins. That’s pretty good.”

So, if the goal of this blog is to foster a conversation among Bucks fans about how to raise another banner up to the Bradley Center rafters, then I think that its important that we have the best information available to tell us how to get that done. For right now, I'm convinced that these "new" statistics... created by economists no less (but genuine bball fans, I'll give them that)... meet that criteria.


At December 20, 2007 at 12:19 AM, Anonymous Anonymous said...

cool, do your thing

At December 20, 2007 at 8:37 PM, Anonymous Anonymous said...

The NBA's eff48 is way too simplistic to be useful, and before you start believing in WOW maybe you should read this (http://www.uncg.edu/eco/rosenbaum/nessis.pdf) and look at this (http://ballhype.com/story/the_foibles_of_formulas_a_quiz/)

Don't forget that Dave Berri's real motivation was to sell books.


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