PDA

View Full Version : Hollinger's "Value-Added" Stat



ttam68
03-25-2009, 05:52 PM
The idea behind Value Added is to take the difference between a given player's performance and that of a "replacement level" talent -- the type of guy who might be sitting at the end of a team's bench, or perhaps in Sioux Falls -- and multiply that difference by the number of minutes that player played. The result shows, theoretically, how many number of points the player added to his team's bottom line on the season.

VA is very useful for award voting in particular, because it allows us to compare players with disparate production and minutes -- say, one player who was brilliant in 60 games and another who was merely good but played all 82 -- and figure out which performance was more productive.

Now for the nitty-gritty.

"Replacement level" is a common term in sports analytics for the level of talent readily available to be picked up off the scrap heap. In NBA terms, it's either a minimum contract guy at the end of the bench or some other team's bench, a veteran off the free-agent scrap heap or a call-up from the D-League.

Nonetheless, analyzing several years of data and looking closely at players who played less than 500 minutes in a season reveals a pattern. The average PER for a "replacement level" player in the NBA is about 11.0, and it varies by position. Power forward is the most replaceable position, with an average replacement level PER of 11.5; the two wing positions are the least, at 10.5 each; point guards, at 11.0, and centers, at 10.6, fall somewhere in between.

Knowing the "replacement level" value at a given position, we can take a player's PER and minutes played and use it to calculate his VA. Chris Paul, for example, has played 2,470 minutes with a PER of 30.06 through Tuesday's games. Since the average replacement level PER for a point guard is 11.0, we take the difference (30.06-11.0) and multiply by his minutes played, returning a product of 47,078.2.

There's one more step. We want VA to mean something, and in this case we want it to be the approximate number of additional points the player has been worth to his team, over the course of the season, relative to a replacement level player. To get to Point A from Point B requires us to divide the result by 67. Yes, 67. Sorry, that's what works. (If you're curious, a point of PER over the course of 2,000 minutes is worth about 30 points to a team, meaning that one point of PER over one minute is worth 1/67th of a point.)

So what we end up with is the formula:

VA = ((Minutes * (PER -- Position Replacement Level)) / 67)

Where Position Replacement Level = 11.5 for power forwards, 11.0 for point guards, 10.6 for centers, and 10.5 for shooting guards and small forwards.

http://sports.espn.go.com/nba/columns/story?columnist=hollinger_john&page=PERDiem-090325

I don't see how he's answering critics of his PER considering this is just a modified form of PER. He still leaves out many elements ignored by PER, and has only really added minutes.

theuuord
03-25-2009, 06:05 PM
http://sports.espn.go.com/nba/columns/story?columnist=hollinger_john&page=PERDiem-090325

I don't see how he's answering critics of his PER considering this is just a modified form of PER. He still leaves out many elements ignored by PER, and has only really added minutes.

you're forgetting position adjustment and replacement level, which is actually a huge difference from the original PER, which is pretty good as a statistical measure already (although, as Hollinger/anyone else says, it's not perfect, and more importantly isn't trying to be).

you didn't quote the FAQ, which I think helps answers some questions:


QUICK VA FAQ

Does this replace PER?

Heavens, no. PER describes a player's per-minute quality of play, and in most situations, that's the thing we care about most. But not all situations; sometimes we want to know more about what a player's season-long value was. MVP voting is the most obvious example, but there are several other situations that come to mind.

So is Bruce Bowen the worst player in the league?

No. He has the worst VA because it becomes negative for players with a PER under the replacement level at their position. Of such players, Bowen has played far more minutes than the rest thanks to his on-ball defensive ability (which PER doesn't measure). Those minutes make his rating even more negative than the rest, dragging him to the bottom of the pile. For genuine awfulness, however, one could argue that Adam Morrison (-47.1) and Stephon Marbury (-1.1) have done as much to hurt their teams as anyone else in the league.

What about leadership and intangibles?

This is a tool to guide the logic of award votes, not one to automatically fill out people's ballots. There are any number of valid reasons why a player who ranks high on this list might be more or less valuable in real life, as I've covered ad nauseam in previous missives: individual defense, locker-room presence and leadership, clutch plays, etc.

I tend to see this as a situation in which the burden of proof matters. As in, if you think Kobe is the MVP and LeBron isn't, and LeBron's VA is nearly double Bryant's, then the burden of proof is on a Kobe voter to explain what in his 2008-09 résumé could overcome such a disparity.

Why don't you just call it VORP?

VORP, adopted from baseball, has been used to describe a number of different methodologies in basketball. While they all do the same sort of thing as this one -- differentiate a player's value from that of a replacement-level player -- there are several different means to that end. It seems pretty easy to confuse onlookers if I'm using one method and calling it VORP and other analysts use different ones, so I thought it best for all concerned if this thing had a name of its own.

Chronz
03-25-2009, 10:17 PM
So basically this is Hollingers version of WARP/VORP?

agnine
03-25-2009, 10:23 PM
Just do what everybody else does, make your own judgement based on what you see. Cause, to me, saying that LeBron, 5 yrs into the league, is better than Hall of Famer Larry Bird (which is what that PER b******t says!) is MORE than a bit premature.

SteveNash
03-25-2009, 10:53 PM
Just do what everybody else does, make your own judgement based on what you see. Cause, to me, saying that LeBron, 5 yrs into the league, is better than Hall of Famer Larry Bird (which is what that PER b******t says!) is MORE than a bit premature.

So did you go blind sometime between the time Bird retired and LeBron was drafted?

Hollinger can arrange his numbers however he wants, they'll never be effective until they become more advanced.