December 08, 2016

Inside the Box, and Doc's Stocks

There is an interesting basketball statistic that has been developed called Box Plus/Minus.  According to its creator, the estimable Daniel Myers,
BPM relies on a player's box score information and the team's overall performance to estimate a player's performance relative to league average. BPM is a per-100-possession stat, the same scale as Adjusted Plus/Minus: 0.0 is league average, +5 means the player is 5 points better than an average player over 100 possessions (which is about All-NBA level), -2 is replacement level, and -5 is really bad.

BPM was created to intentionally only use information that is available historically, going back to 1973-74. More recently there has been more information gathered, both in box scores and via play-by-play, but in order to create a stat with historical usefulness, those stats have been ignored for BPM. In other words – it is possible to create a better stat than BPM for measuring players, but difficult to make a better one that can also be used historically.

Basketball Reference helpfully provides a list of the best 250 Box Plus/Minus player seasons since 1973-74.  So there you go - a quick and easy way to compare players.  One way is to look at who has the most of those 250 seasons:

  • 12
    • Charles Barkley
    • Karl Malone 
    • LeBron James
  • 10
    • Michael Jordan
  • 9
    • Chris Paul
    • Clyde Drexler
    • David Robinson
    • Kevin Garnett
  • 8
    • Julius Erving
    • Larry Bird
    • Magic Johnson
    • Shaquille O'Neal
  • 7
    • Kareem Abdul-Jabbar
    • Scottie Pippen
    • Tim Duncan
  • 6
    • Dwayne Wade
    • Tracy McGrady
  • 5
    • Hakeem Olajuwon
    • Manu Ginobli
  • 4
    • Bob Lanier
    • Dirk Nowitzki
    • Fat Lever

It's unclear to me why power forwards dominate the top of the list, but otherwise this seems pretty intuitive.  I took those seasons and sorted them by player, and then in descending order of Box Plus/Minus score.  Some interesting patterns emerge.  For example, who was better, Bird or Magic?  Eh, they were about the same.  So was Doctor J.  And Kareem?  About the same, but a bit better at his peak:

The statistic seems good for comparing players within an era, but less so across eras.  For example, eight of the top ten seasons on the list were compiled after 2007 (the other two were Jordan).  Also, as modern training methods and arthroscopic surgery came in, players were able to sustain their careers longer, e.g.,

Moreover, a couple of guys were able to combine longevity with a hitherto unheard-of ability to fill up a boxscore:

But perhaps the most interesting thing about Box Plus/Minus is who it leaves out - mostly outstanding players who are nevertheless somewhat one-dimensional:

  • Kobe Bryant only has three of the top 250 seasons (highest:  6.4 in '03...comparable to Scottie Pippen's 1990-91 campaign).
  • Allen Iverson does not appear.
  • Isaiah Thomas does not appear.
  • Kevin McHale does not appear.
  • Moses Malone does not appear (except on the ABA list).
Tim Duncan (7 seasons) and Hakeem Olajuwon (5) show up on the list, but with disappointingly low scores.  The statistic's author explains that Box Plus/Minus probably understates the value of a great defender:
There are limitations on all box score stats...on defense the box score is quite limited. Blocks, steals, and rebounds, along with minutes and what little information offensive numbers yield about defensive performance are all that is available. Such critical components of defense as positioning, communication, and the other factors that make Kevin Garnett and Tim Duncan elite on defense can't be captured, unfortunately. 
What does this mean? Box Plus/Minus is good at measuring offense and solid overall, but the defensive numbers in particular should not be considered definitive. Look at the defensive values as a guide, but don't hesitate to discount them when a player is well known as a good or bad defender.

Hmmm.  So, for example, in his magisterial Big Book of Basketball, Bill Simmons calls Doctor J a "surprisingly subpar defender."  Which I hadn't heard before, and, as near as I can tell is completely false.  Simmons provides us with a helpful tool tools elsewhere in the book, as he tries to explain the awesomeness that was Hakeem Olajuwon:
If we created a stat called “stocks” (just steals plus blocks), Hakeem topped 300-plus stocks with at least 100 blocks/ steals in twelve different seasons (nearly double anyone else), notched 550 in 1990 (the only time anyone’s ever topped 500) and finished with 1,045 combined in ’89 and ’90 (the only time anyone ever topped 1,000 combined in two years). During his peak, Dream caused five turnovers per game along with countless other layups and runners he probably affected from game to game. (Note: I like “stocks” because it gives you an accurate reflection of his athletic ability and the havoc he wreaked on both ends. No modern center was better offensively and defensively than Dream. I should have come up with “stocks” four hundred pages ago. Crap.) 
There also a footnote.  It says:
The complete list since ’74 (2x minimum): Hakeem (12x), Robinson (7x), Ben Wallace (4x), Julius Erving (7x), Kareem (3x), Ewing (3x), Bobby Jones (3x), Jordan (2x), Josh Smith (2x), Andrei Kirilenko (2x), Elvin Hayes (2x), Terry Tyler (2x). MJ is the only guard on the list.
Emphasis added.

Perhaps this table will further clarify matters:

It says here that Julius Erving was as valuable in his career as Bird or Magic, a better defensive player than either of them, and the best defensive small forward of his era.  All other arguments are invalid.

Get that weak shit out of here


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