APBRmetrics

[acollard]

This is to serve as a more thorough explanation and technical discussion of the regression I ran and the findings it gave from my post at DailyThunder . It takes some methodology from the article I asked about a couple weeks ago, Playing for Keeps by K. Stiroh.

From prosportstransactions.com I collected contract information for every player who played 500 minutes in at least two seasons from 1998-2010. I broke these down into 3 categories, unrestricted free agents, free agents, and post long contract. I ignored extensions for the pre-contract effects, because it is incomplete to include everyone who signed an extension, everyone who is eligible must be used instead. This gave 4106 player seasons with 1033 contract observations. (Thanks to DsMok1 for the spreadsheet he shared in the Advanced SPM thread).

The basic regression was dvar= ai*age+ai2*age^2+player+rfa+ufa+post

Where player is a dummy variable for each player, rfa is a dummy variable for if the player will enter restricted free agency at the end of the year, ufa is the same but for unrestricted free agents, and post is a dummy variable coding for the year after a contract is signed that is four years or more in length (If I had to guess, I probably didn't catch all of these). The results of these regressions for some dependent variables I picked are below. I didn't use dummy variables for team and year because although they helped improve the R-squared a little, they didn't change results besides WS much (because WS are tied a lot to team effects) and I worried that I might have been overfitting.


Sorry for the lack of table formatting, I don't have time to figure it out now. DT has it formatted nicely.

[Jon Nichols]

A long time ago, using PER and much less sophisticated methods, I found similar results. However, I did find that average PER decreased in the year after signing a new contract. Here's a link:

http://basketball-statistics.com/playingforthemoney.html

[acollard]

Thanks for the link, John.

Two things are different between our studies. I included one-year links, because the one year qualifying offer is considered a new contract and it includes some significant players, and i figure the minutes/season restriction would be good enough. I

i also only included those on longer length contracts (+3 years) because I don't think people often view 2 or 3 year contracts as albatrosses. Here's what my regression gives for PER:

[acollard]

perhaps this table is a little clearer

[Ed Küpfer]

[acollard]

Thanks for the link, I'm sure I'll find that extremely useful.

I'm sorry that I made that conjecture about individual offensive rating vs individual defensive rating without explanation. My reasoning is that individual offensive rating just being ortg= (pts scored by player)/ ( 100 possessions used by player) would show individual player improvement more than defensive rating, which is affected a lot by the teammates around the player in question.

[acollard]

[quote="Ed Küpfer"]