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Re: Dick Cramer's baseball work -- Evaluating history vs today

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  • Mike G
    ... much ... that ... What I found was that in every non-expansion NBA season, minutes are reduced for the average player (from the previous season). These
    Message 1 of 8 , Jun 25, 2003
      --- In APBR_analysis@yahoogroups.com, "Michael Tamada" <tamada@o...>
      wrote:
      > > [DeanO:]
      > > Cramer wrote, "direct comparison
      > >cannot be made for seasons more than 20 years apart; few played
      much
      > >in both periods, say, 1950 and 1970. But these seasons can be
      > >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
      that
      > MikeG did with minutes played statistics and how they vary from
      > season to season.

      What I found was that in every non-expansion NBA season, minutes are
      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
      competition.

      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
      cumulative norm.

      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'
      > minutes from year-to-year, and DeanO found consistent downward
      trends in
      > players' FG%. Could be due to strength of competition, could be
      due to
      > league strategies, but I'm guessing that some of it is due to
      players
      > having a few years of increase followed by many more years of
      gradual
      > 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
      home.
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