Re: Dick Cramer's baseball work -- Evaluating history vs today
- --- In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
> > [DeanO:]much
> > Cramer wrote, "direct comparison
> >cannot be made for seasons more than 20 years apart; few played
> >in both periods, say, 1950 and 1970. But these seasons can bethat
> >compared indirectly by comparing 1950 to 1955 to 1960, etc., and
> >adding the results."
> Interesting, it's similar to what I've been proposing (look at long
> career players such as Hayes and Havlicek and how their stats
> changed over time) and sounds like it's also similar to the work
> MikeG did with minutes played statistics and how they vary fromWhat I found was that in every non-expansion NBA season, minutes are
> season to season.
reduced for the average player (from the previous season). These
minutes are presumably taken up by rookies, who play more minutes
than guys in their final seasons.
Whether you look at consecutive seasons or the cumulative effects of
5 seasons, there is no conclusion available about whether declining
minutes are more the result of (1) aging, or (2) increasing
What I did find was that there was significant re-apportionment
(inflation) of minutes in expansion years. This to me implies a
certain reduction in competition for those years. Presumably, the
competition remains (partly) diluted until the curve returns to the
It's in the definition of this 'norm' that we all get our prejudices
out on the table. If we 'know' the competition is stiffer in the
present era, then the reducing-minutes phenomenon is primarily the
result of increasing competition.
My gut feeling is that there is so much 'noise' in the eral
differences of travel, training, etc, that we may as well resign
ourselves to an arbitrary definition, such as 1967 = 1977, draw a
straight line thru those, and extrapolate forwards and backwards.
So, if the cumulative annual ups-and-downs in average minutes yields
an annual average over that interval of, say, .9785, then that can
be the annual standard that accounts for 'aging'; and any departures
can be attributed to changes in competitive level.
Using such a short baseline (11 years) could yield startling
suggestions for 1953 and 2003, of course.
> MikeG found consistent downward trends in players'trends in
> minutes from year-to-year, and DeanO found consistent downward
> players' FG%. Could be due to strength of competition, could bedue to
> league strategies, but I'm guessing that some of it is due toplayers
> having a few years of increase followed by many more years ofgradual
> decline in many of their stats.Actually, it shouldn't depend on the shape of the trajectory, but
only on the fact that a player whose rookie-year minutes were 2000
and whose 10th-and-final-year minutes were 1000 shows an average
loss of 100 minutes per year.
Whether he peaks at 2000 or 3000 minutes, the average for his career
comes out to the same thing. No difference whether the trajectory
is smooth or all ups-and-downs.
I spent a couple of hours tracking year-to-year changes in (1) FG%
and (2) scoring % (points divided by attempts).
I've got it tracked by NBA season (1952-2002) and by players' years-
in-the-league. There are a couple of complications, though.
A 15-year player has a much different trajectory over his first 5
years than does a 5-year player. The data is skewed very much to
the short-career player.
Rather than attempting the monumental task of categorizing 2nd-year
players from 1995, 3rd-year players from 1995, etc (some 15*60
subcategories); I just grouped them into 2-5th-year, 6-10 year, 11-
15 year. (Beyond 15 years is insubstantial sample.)
I will post this In Some Form, if anyone is interested. When I get