Math & Basketball: Astronomy used to be just watching pretty stars, too
BASKETBALL ON PAPER
Dean Oliver
Author, Basketball on Paper Consultant to the Seattle Supersonics Using Sports to Teach Math Symposium Seattle, WA May 13, 2006
1
Some History
Every science we have today was once just “interesting”
Chemistry Biology Astronomy Finance and economics Physics
Interesting + math = science Math = Science - Interesting
Dean Oliver deano@rawbw.com
BASKETBALL ON PAPER
2
Language and logic first…
Score a game
5 CHI UTA 6 CHI UTA 8 CHI UTA 8 CHI UTA 8 CHI UTA 23D/ 91- A 32R 12D/ 3 32 12D 14- X 13R 9D/ 33 23 33 13F32(1)X* 12D/ 14 32 3- R 00R 12D 32++B 33D/ 91 23D 33 23++A 12D/ 32++2 33 / 9D 23D- 3 13R- L 13F12(1) 23 91 33 9 23D- B 14R 32D 12D/ 3 32DF91(1)X* 33D/ 23D 9 33 23 13 9-Y 3RD / 12 14 32 12++R
4 6 8 9 11
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
3
…Then counting…
How many lines? How many lines with a score? How many touches? How many post-ups? How many offensive rebounds off missed free throws?
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
4
…And Analysis
Same number of possessions…
Equivalence scale on possessions Per available rebound
Points per possession Four Factors
Basketball on Paper
Effective shooting percentage Turnovers per possession Offensive rebounding percentage Free throw rate
Dean Oliver deano@rawbw.com
BASKETBALL ON PAPER
5
Stories to tell
Grades
Tactics
Is ___ the next Michael Jordan? Who should we draft? Is __ a good coach? Why so many offensive rebounds? Is offense better when forcing more touches? Should we double team the post? Is it easier to shoot an open jump shot from 3pt range or a contested one from 2pt range? Should a team pay more to win? When do players get their big paycheck?
Dean Oliver deano@rawbw.com
Financial
BASKETBALL ON PAPER
6
The Possession Framework
Possessions are equal What you do per possession is what matters Possession ends:
Missed shot rebounded by defense Made field goal, no free throw Turnover Made last free throw
Possession formula:
(FGA – FGM – OR) + FGM + TOV + 0.4*FTA
Dean Oliver deano@rawbw.com
BASKETBALL ON PAPER
7
Floor% and Play%
Floor%: Percentage of possessions on which there is a score
Scoring Possessions/Possessions
Play%: Percentage of “plays” on which there is a score
Scoring Possessions/Plays
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
8
Four Factors
Effective Field Goal Percentage
(FGM + 0.5 * FG3M)/FGA
TOV/Poss OR/(OR + OppDR) FTM/FGA
Dean Oliver deano@rawbw.com
Turnover Percentage
Offensive Rebounding Percentage
Free Throw Ratio
9
BASKETBALL ON PAPER
Test!
Seattle 1998
eFG%: 52.1% FT%: 72% TOV%: 15.7%
eFG%: 51.9% FT%: 68% TOV%: 16.2%
Dean Oliver deano@rawbw.com
LA Lakers 1998
Better offense?
10
BASKETBALL ON PAPER
Answers
Lakers had better offense
111.9 pts/100 poss to 111.4
Shot worse from everywhere Rebounded worse Turned ball over more Shot 600 more free throws! More shots of overall higher percentage shot
Dean Oliver deano@rawbw.com
How?
But…
BASKETBALL ON PAPER
11
More Framework: Estimating Wins
Wins come from point difference (points/possession) Wins ~
A*(points – points allowed) + 0.5 B*(pts/poss – pts allowed/poss) + 0.5 pointsC/(pointsC + points allowedC)
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
12
Wins from a Bell Curve
Figure 2: Distributions of Home and Road Scores, 2000-2001 and 2001-2002 Seasons
20% 18%
Percentage of Games
16% 14% 12% 10% 8% 6% 4% 2% 0% Road Scores Home Scores
60 61 -6 5 66 -7 0 71 -7 5 76 -8 0 81 -8 5 86 -9 0 91 -9 96 5 -1 10 00 11 10 05 61 11 10 11 11 15 61 12 20 11 12 25 613 0 >1 30
Score
<=
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
14
Bell Curve Principles
Consistency matters Playing up or down to opponent matters Don’t blow teams out by too much Unbiased referees change odds
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
15
Player Evaluation
What makes a good player?
Almost the same as what makes a good
team Roles/Interactions affect everything
Volume of shots Communication Coordination
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
16
Decreasing Marginal Returns
Player Skill Curve (Averaged)
45% 40% 35% 30%
% Tm Poss
25% 20% 15% 10% 5% 0% 75 85 95 105 Rating 115 125 135
J. Stackhouse
A. Iverson
M. Jordan
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
17
Optimize Lakers’ Offense
Unbalanced offense
Player Bryant Odom Parker Brown Walton Totals % Tm Poss Off. Rtg. 36% 114 19% 111 15% 107 14% 106 16% 101 100% 109
More balanced offense
Player Bryant Odom Parker Brown Walton Totals
% Tm Poss Off. Rtg. 26% 119 22% 103 18% 99 16% 98 18% 95 100% 104
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
18
Overall Player Ratings
“Ratings” aren’t objective What are you measuring? Offense, defense, (in)tangibles
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
19
Other Projects
Best player to step up to help offense What to emphasize on defense How will players develop? How to help them? What tactics to take against good teams? What tendencies do teams have to take advantage of? How to predict player performance from another league?
Dean Oliver deano@rawbw.com
BASKETBALL ON PAPER
20
Work with 82games.com
They do research projects
Ahead by 3, foul or defend? Does Steve Nash help his teammates? What does Kobe Bryant do in the clutch? How likely is it to make a shot after making the previous one?
BASKETBALL ON PAPER
Dean Oliver deano@rawbw.com
21