Wednesday, October 10, 2007

The front page of ESPN's NBA site is the following:

Hollinger's Player Ratings
How do they rate?
John Hollinger has the 2007-2008 projections for every NBA player, from 1 to 328.

Within this feature Hollinger rates all NBA players using his PER metric, which is the official player rating of the NBA.

It's a pretty good metric, showing how NBA players rank based on their objective game stats. There's just one big problem, though.

A player gets a point for each basketball point scored, so a 2-point basket gives a player 2 points.

A missed shot is -1 points, so if a player shoots on two consecutive possessions and makes just one basket, his net point total is +1.

At this point the player is shooting 50%, which is good (particularly if he is a guard), so giving him a point seems valid.

However, if the player shoots a third basket and again misses, he is now shooting 33% and his net point total is 0.

33% shooting is horrendous, and each year no players with significant minutes shoot that poorly. However, a player shooting at that rate is not penalized in the PER system.

Therefore, if a player shoots above 33% - say 34% or 35%, which is still terrible - he will receive positive net points.

So as long as a player shoots at least 33%, the more shots he takes the higher his PER will be.

I didn't figure this out myself of course, I owe all this to the Wages of Wins, a site I have mentioned exhaustively. They have developed a better system of player evaluation, in part because a missed basket is worth -2 points instead of -1, but more importantly because they linked every statistic to actual team wins and weighed them appropriately. It is a far more accurate system and more people need to know about it. I'm just trying to do my part.

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