3693Re: Dampier (was Article from _The Economist_)

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• Apr 7, 2004
wrote:
..
> if we're looking at a 29 year old Dampier or whoever, and trying
to predict
> what his age 30, 31, etc. stats will look like, then we don't want
to look
> at the overall average for 30-year olds (or 30-year old all-
NBAers, or
> whatever group). Instead we'd want to look at what the typical
*change
> in performance* is for a 30-year old, compared to what he did as a
29-year
> old.

It so happens I've been doing something like this.

I also corrected for what might be considered a "bias" in a manley-
type production figure: the NBA has overall been
losing "productivity", on a per-game basis. Thus, all 30-year-olds
have been around long enough to see a significant decrease in
production, among all players.

My figures show a per-game/per-team high around 144 in the mid-'80s,
which has since dropped to about 125. Not sure of the manley
formula Ed used, but I'm applying one equally to teams and
individuals; using a formula like the one BobC layed out.

Briefly, I see an average change based on age that looks like this:

%inc is average increase (decrease if negative) of the age group
that went on to play the next year, in "manley credits".

SS# is sample size (player-seasons since 1978)

age %inc SS#
18 .897 3
19 .332 12
20 .353 30
21 .130 94
22 .224 360
23 .113 729
24 .044 771
25 -.011 734
26 -.020 700
27 -.065 625
28 -.071 562
29 -.094 519
30 -.129 453
31 -.171 374
32 -.125 274
33 -.181 203
34 -.183 142
35 -.178 91
36 -.246 62
37 -.319 36
38 -.236 20
39 -.026 8
40 -.246 3
41 -.271 2
42 -.604 1

For 519 players age 29 who went on to play in their 30th year, an
average loss of 9.4% has occurred.

Earlier studies have shown an erosion of minutes, on average, from
year to year in a player's career. No doubt, this is a part
contributor in the total production a player loses. I'll be back
with per-minute losses due to aging.
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