APBRmetrics

J.E. wrote:Based on early research results from the effect of aging on RAPM values, this chart and the fact that recent NBA championship teams have been rather old, it is my opinion that a player's peak of impact is closer to 28/29 years than 25/26.

Possibly, but I'm not sure about it.

Your prior informed RAPM is not a good data point for that anymore, because the way you have combined them biases the older player's RAPM values up significantly, at the expense of the younger player's RAPM values.

J.E. wrote:...the fact that recent NBA championship teams have been rather old, it is my opinion that a player's peak of impact is closer to 28/29 years than 25/26. ..
Younger players also care more about money, probably because they just haven't made that much yet, compared to older players. And I think they know that better BoxScore statistics lead to bigger contracts..

Excellent. Dan Rosenbaum noticed that older players have better plus-minus relative to their stats, back when he was the first to delve into the correlations between stats and effectiveness.

But maybe there's a little bit of circular reasoning in the quote above. As players age, they've made their fortunes and want a ring. So they coalesce and create championship contenders. If they aren't actually colluding (last year's Miami big3), they're settling for less money on a better team.

The key to reconciling stats and wins, I believe, is to scale boxscore stats to opponent averages. A point is worth more when points are scarce. A rebound, likewise.
And we may presume that as players gain experience, they improve at basics like blocking out for the rebound and playing team defense. So it may well be that it's harder to score and rebound against older teams.

Maybe Daniel already addressed it but isn't there a selection bias for aging, because older players still in the league, say on their third or even fourth contract are the ones that made it that far and presumably had more talent. Younger players with less talent are not necessaily still playing at age 30+.

EvanZ wrote:Maybe Daniel already addressed it but isn't there a selection bias for aging, because older players still in the league, say on their third or even fourth contract are the ones that made it that far and presumably had more talent. Younger players with less talent are not necessarily still playing at age 30+.

The selection bias issue to be concerned about is not that one--that's just a part of the distribution of players; some are better, some are worse.

Here's an issue to worry about: at the tail end of careers, when players are marginal, only the "lucky" players get another chance. Then, the next year, they are "unlucky", and that is the end of their careers. Thus the YtY change is biased high--the players that were "unlucky" in year 1 never get a chance to be "lucky" in year 2, to counter balance the "lucky"->"unlucky" sequence. Now, in basketball luck is less significant than in baseball, so this isn't the huge issue it is with MLB aging curve generation, but it still must be accounted for.

Here's a really interesting post from wiLQ at Weakside Awareness, evaluating last year's predictions:

http://weaksideawareness.wordpress.com/ ... n-2010-11/

John Hollinger bested everyone...essentially tying Vegas. (Once again proving the wisdom of the betting market beats single prognosticators).

Of course I was using WP at the time. Oh, well.

DSMok1 wrote:Here's a really interesting post from wiLQ at Weakside Awareness, evaluating last year's predictions

Thanks for the plug... by the way, will it be too strange/silly to revisit previous seasons?
For example, I wonder about author's consistency and it's not fun to wait a couple of years to collect more data when there is some available from the past.

wilq wrote:

DSMok1 wrote:Here's a really interesting post from wiLQ at Weakside Awareness, evaluating last year's predictions

Thanks for the plug... by the way, will it be too strange/silly to revisit previous seasons?
For example, I wonder about author's consistency and it's not fun to wait a couple of years to collect more data when there is some available from the past.

I'd be happy to see it... I don't think I personally had previous predictions, however.

Does anyone adjust for coaching changes?

I think Casey (Toronto) is going to have more positive influence than whoever they had before
Frank (Detroit) cannot be worse than Kuester
Houston has a different coach, but I'm not sure if that makes a difference
Minnesota replaced Rambis with Adelman, probably an improvement
Corbin (Utah) is probably a bit worse than Sloan
The Lakers have Brown now instead of Jackson, I don't think it makes too much of a difference
Golden State has a new coach. Many believe he will *$%&, but obviously we can't tell yet.

All in all, I think it's probably OK to ignore coaching changes for most teams EXCEPT Toronto and Detroit, because Casey did great things in Minnesota (and probably Dallas) and Kuester was nothing short of a disaster in Detroit


Another subject:
Many players, who RAPM believes they're at least decent, do not have jobs at the moment. These include: Julian Wright, Quinton Ross, Fesenko, Othyus Jeffers, Alexis Ajinca, Cartier Martin, Bobby Simmons

That may be for multiple reasons:
-RAPM, obviously, only gives an estimate. We can't be sure for any player that the rating he was given is actually close to his actual skill.
-These players are really not good in a general basketball sense, but were put into the game by their coaches *only* in situations the coaches knew they players could succeed in. These situations may be rare
-Most of these players are neither flashy nor shot creators. In fact, most of their value comes on the defensive end. Good defense that doesn't involve highlights can be more easily overlooked than good offense

I think, if I'm a team under the cap and I don't plan on tanking this season, I would give everyone of these a contract (probably a minimum contract because nobody else seems to want them) and then see how it plays out. Even more so when I'm close to contending and already have 2-3 shot creators on my team

Predictions made or at least tracked here:

2008-9 viewtopic.php?f=2&t=121&hilit=predictions

2009-10 viewtopic.php?f=2&t=179&hilit=2010+pred ... &start=105

2010-11 viewtopic.php?f=2&t=124&hilit=predictions

Few were in these lists every year but John Hollinger, Vegas and I (using screenname Mountain then Crow) were in the top 3 here twice in 2 tries.

By WinShares Julian Wright is a top 10 similar to Yi Jianlian.
By RAPM Wright was about a top 60 performer in the league last year. Like Yi his RAPM has risen year to year but it has risen from -2 to +2. a higher starting point and a higher achievement to date.

Wright looked promising by boxscore stats his rookie season but since regressed on many of them. His improvement in RAPM appears to have come in team level defense or at least his team level defense on/off.

A team looking to the future might want to try to experiment with him as a scoring (not shooting) SG (probably as a bench player) at some point if they have shooting at PG and SF. I'd guess that he might have been looking for more money than he was being offered. If so, he will have to change his expectations. Lack of a 3 pt shot and poor FT% and increasing turnovers are among the factors hurting his case. But maybe some devotee of RAPM improvement or team defense or both will give him a look.

I didn't search far but Phoenix might be one team who might want to at least consider him, though there may be better options.

Is there a single source that shows current rosters? I need to get down to finalizing.

I don't know who has it most up to date but this is one fairly good option:
http://www.eskimo.com/~pbender/rosters.html

Crow, thanks. They do still show Krstic for the Celtics and Pachulia with the Hawks, no disclaimers.

Does anyone adjust for coaching changes?

A couple years back I adjusted for teams who have habitually won more or fewer games than their point differential would predict. Yes, there are significant tendencies. But it likely didn't help my predictions much.

She has been better with adds than deletions. The final rosters will be available tomorrow or the next day. A projection a few days into the season wouldn't be a problem in my eyes. I am probably not going to do one this season.