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Re: [APBR_analysis] Standard deviation,Part Two

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  • John W. Craven
    ... Year FG% STDev STD% Notes 1947 27.9 3.45 12.402 1948 28.6 3.11 10.835 1949 32.9 3.91 11.905 1950 34.0 4.01 11.827 First year of the NBA; old BAA
    Message 1 of 5 , Dec 28, 2002
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      On Sat, 28 Dec 2002, John W. Craven wrote:

      > Note: I looked at all players in a season with at least 300 FGs attempted. FG% is not the actual league FG%, but the average of all the FG%s of the players used in each year's study.
      >
      Year FG% STDev STD% Notes
      1947 27.9 3.45 12.402
      1948 28.6 3.11 10.835
      1949 32.9 3.91 11.905
      1950 34.0 4.01 11.827 First year of the NBA; old BAA expands from 12 to 17 in merger
      1951 35.7 3.87 10.829 Down to 10 teams by year's end
      1952 36.8 4.01 10.890
      1953 37.2 3.54 9.516
      1954 37.3 3.49 9.376 Bullets disband; 8 teams by year's end
      1955 38.2 3.47 9.083
      1956 38.3 3.29 8.597
      1957 37.7 3.50 9.283
      1958 37.9 3.60 9.496
      1959 39.1 3.41 8.708
      1960 40.3 3.98 9.840 Wilt's first season
      1961 40.4 4.31 10.667
      1962 41.7 4.16 9.967 NBA expands to 9 teams (Chicago Packers)
      1963 43.8 4.10 9.373
      1964 42.6 3.71 8.712
      1965 42.2 4.10 9.711
      1966 43.0 3.65 8.488
      1967 43.8 3.97 9.079 Expansion to 10 teams (Baltimore Bullets)
      1968 44.4 4.03 9.105 Expansion to 12 teams (Seattle, San Diego), 1st year of the ABA
      1969 43.9 3.91 8.918 Expansion to 14 teams (Milwaukee, Phoenix)
      1970 45.4 4.00 8.797
      1971 44.6 3.83 8.581 Expansion to 17 teams (Buffalo, Cleveland, Portland)
      1972 45.5 4.07 8.940
      1973 45.6 4.44 9.728
      1974 46.0 3.18 6.909 What's going on here?
      1975 45.8 3.35 7.324 Expansion to 18 teams (New Orleans)
      1976 45.8 3.59 7.831 Last year of the ABA
      1977 46.3 4.03 8.716 Merger expands NBA to 22 teams
      1978 46.7 3.99 8.553
      1979 48.3 3.85 7.969 Sonics win their only championship

      The 1979-80 season was the first year of the three-pointer. I'm going to chart both unadjusted FG% and effective FG% from here on out.

      1980 47.0 4.16 8.670 48.4 3.98 8.225
      1981 48.6 4.37 9.003 48.9 4.24 8.695
      1982 49.1 4.26 8.675 49.5 4.04 8.183
      1983 48.6 4.44 9.152 48.9 4.30 8.802
      1984 49.1 4.24 8.632 49.4 4.10 8.289
      1985 49.4 4.01 8.115 49.9 3.88 7.780
      1986 48.9 4.30 8.797 49.4 4.12 8.328
      1987 47.9 4.33 9.046 48.7 4.14 8.495
      1988 47.9 4.12 8.586 48.9 3.98 8.120
      1989 47.6 4.04 8.483 48.9 3.93 8.040 Expansion to 24 teams (CHA, MIA)
      1990 47.6 4.19 8.797 48.9 4.05 8.290 Expansion to 26 teams (MIN, ORL)
      1991 47.3 4.24 8.940 48.7 4.05 8.317
      1992 47.3 4.29 9.079 48.6 4.21 8.646
      1993 47.4 3.78 7.975 49.0 3.63 7.402
      1994 46.6 4.33 9.281 48.5 3.81 7.852
      1995 46.9 4.53 9.649 50.2 4.21 8.380
      1996 46.4 4.39 9.449 50.2 4.17 8.314 Expansion to 28 teams (TOR, VAN)
      1997 45.6 4.73 10.366 49.5 4.12 8.309
      1998 45.0 4.30 9.565 47.9 4.04 8.438
      1999 44.2 3.86 8.731 47.1 3.89 8.252 Strike; schedule limited to 50 games
      2000 44.9 4.22 9.390 48.1 3.82 7.946
      2001 44.1 4.06 9.210 47.2 4.09 8.663

      Anyway, there you go. A couple of observations:

      1. There seems to be a significant increase in competitive balance in the first ten years of the league, and then after a slight decrease in the early 60s, it flattens out through the 60s and 70s, and after the merger with the ABA remains more or less static.

      2. The ABA merger, instead of increasing balance like I thought it would, drastically reduced it. Interesting.

      3. What's up with the 1973-4 season? According to this metric, it's the most competitive by far in NBA history. Overall, the area right around the ABA merger scored the lowest; 4 seasons had scores of under 8 from 1974 to 1979.

      4. With the advent of the 3-point shot, straight FG% becomes more and more unwieldy, this trend climaxing in 1996-7, when it scored over 10 - the first time it had done so since 1960-61 (wasn't the 3-point line moved back that year?). However, effective FG% remained in line with the established norms of the late 1970s. 1985, 1993, 1994, and 2000 all scored under 8.

      5. No matter which way you look at it, the league was more competitive (according to this metric) in 1986-7 than 1954-5. If you think that effective FG% is a better measure after the advent of the three-pointer like I do, then there is a large bit of difference.

      6. I expected the 1990s to be quite a bit less competitive than the 1980s. Go figure.

      7. Expansion doesn't seem to have that large of an effect on the scores. There was a spike at about the time the Grizzlies and Raptors entered the league, but it happened a full year before their inception. There was also a slight rise in the early 90s that can be attributed to the 4 new teams then, but that effect was gone by 1993. 1967 and 1968 both saw slight decreases in competition. 1962, 1969, and 1971 both saw _increases_ in competition, though. The only significant expansion-wrought change seems to be the ABA merger.

      John Craven
    • harlanzo <harlanzo@yahoo.com>
      ... the 1980s. Go figure. when i think about out this seems to make sense. the lakers, celts were great but playoffs were rarely stacked with good teams.
      Message 2 of 5 , Dec 28, 2002
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        --- In APBR_analysis@yahoogroups.com, "John W. Craven"
        <john1974@u...> wrote:
        > On Sat, 28 Dec 2002, John W. Craven wrote:
        > Anyway, there you go. A couple of observations:
        >
        >>

        >

        >
        > 6. I expected the 1990s to be quite a bit less competitive than
        the 1980s. Go figure.

        when i think about out this seems to make sense. the lakers, celts
        were great but playoffs were rarely stacked with good teams. bucks
        were good and sixers and their moments too. on a whole though,
        their were few playoff surprises except maybe la losing to sampson
        (i exclude upsets in the old 3 game series format as too small a
        sample size to be meaningful). an examination of the playoffs does
        seems to indicate that more competitve teams were springing up near
        the end of the 80s. in contrast, the 90s seemed to have a bunch of
        good teams (though they had only one team consistently as good as
        the lakers and celts).

        >
        > 7. Expansion doesn't seem to have that large of an effect on the
        scores. There was a spike at about the time the Grizzlies and
        Raptors entered the league, but it happened a full year before their
        inception. There was also a slight rise in the early 90s that can be
        attributed to the 4 new teams then, but that effect was gone by
        1993. 1967 and 1968 both saw slight decreases in competition. 1962,
        1969, and 1971 both saw _increases_ in competition, though. The only
        significant expansion-wrought change seems to be the ABA merger.
        >

        you might remember that the nba moved in the 3-point line for the 93-
        94 and the 94-95 seasons. they returned in the 95-96 (the expansion
        year). this might account for this weird hiccup before expansion.
      • Mike G <msg_53@hotmail.com>
        ... John, I don t see anything here. Yes, the standard deviation approach sounds like it may have merit. But the lack of correlation with expansion seasons
        Message 3 of 5 , Jan 1, 2003
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          --- In APBR_analysis@yahoogroups.com, "John W. Craven"
          <john1974@u...> wrote:
          >.....
          > Year FG% STDev STD% Notes
          > 1947 27.9 3.45 12.402

          ....

          > 2001 44.1 4.06 9.210 47.2 4.09 8.663

          John, I don't see anything here. Yes, the standard deviation
          approach sounds like it may have merit. But the lack of correlation
          with expansion seasons seems not to support the theory.

          > ...
          > 3. What's up with the 1973-4 season?

          Completely wack. I'd check my math.


          > .....
          > 6. I expected the 1990s to be quite a bit less competitive than
          the 1980s. Go figure.

          I think the league has gone downhill since the early or mid-'90s.
        • John W. Craven
          ... I agree. I ll re-work this with something that takes into account foul shots, and then try to look at players with more shot attempts per year than 300.
          Message 4 of 5 , Jan 1, 2003
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            On Wed, 1 Jan 2003, Mike G <msg_53@...> wrote:

            > --- In APBR_analysis@yahoogroups.com, "John W. Craven"
            > <john1974@u...> wrote:
            > >.....
            > > Year FG% STDev STD% Notes
            > > 1947 27.9 3.45 12.402
            >
            > ....
            >
            > > 2001 44.1 4.06 9.210 47.2 4.09 8.663
            >
            > John, I don't see anything here. Yes, the standard deviation
            > approach sounds like it may have merit. But the lack of correlation
            > with expansion seasons seems not to support the theory.

            I agree. I'll re-work this with something that takes into account foul shots, and then try to look at players with more shot attempts per year than 300.

            >
            > > ...
            > > 3. What's up with the 1973-4 season?
            >
            > Completely wack. I'd check my math.

            I did, and it's still damn low. Note that the two years right afterward were also two of the lowest in the study.

            >
            >
            > > .....
            > > 6. I expected the 1990s to be quite a bit less competitive than
            > the 1980s. Go figure.
            >
            > I think the league has gone downhill since the early or mid-'90s.

            That's what I expected to see show up as well. I'll see if that trend shows up when I re-do this.

            John Craven
          • Dean Oliver <deano@rawbw.com>
            ... I ve done competitive balance stuff before and seen all the economists stuff, too. I believe that I and they also have this season being very
            Message 5 of 5 , Jan 2, 2003
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              --- In APBR_analysis@yahoogroups.com, "Mike G <msg_53@h...>"
              <msg_53@h...> wrote:
              > > ...
              > > 3. What's up with the 1973-4 season?
              >
              > Completely wack. I'd check my math.

              I've done competitive balance stuff before and seen all the
              economists' stuff, too. I believe that I and they also have this
              season being very competitive. I'll try to check soon.

              DeanO
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