I have completed another of my objective NBA Power Rankings using the “Relative Winning Percentage” formula.

RWP compares each NBA team’s pythagorean* winning percentage at home and its pythagorean winning percentage on the road to the rest of the NBA’s pythagorean winning percentage against the same home schedule and the rest of the NBA’s pythagorean winning percentage against the same road schedule. Each team is then ranked according to the average of the two comparisons plus .500%. That is what I call its “Relative Winning Percentage”.

**Sidebar on what the term “Pythagroean” means as used in RWP (explained by basketball-reference.com**):

**W Pyth**- Pythagorean Wins; the formula is G * (Tm PTS
^{14}/ (Tm PTS^{14}+ Opp PTS^{14})). The formula was obtained by fitting a logistic regression model with log(Tm PTS / Opp PTS) as the explanatory variable. Using this formula for all BAA, NBA, and ABA seasons, the root mean-square error (rmse) is 3.14 wins. Using an exponent of 16.5 (a common choice), the rmse is 3.48 wins. Why do I use this instead of just using straight winning percentage? I want to eliminate luck to the greatest extent possible. I’m trying to measure relative strength, not fortuity.

**RWP Example**:

Using Pythagorean numbers, NBA home teams beat Team X’s home opponents .673% of the time, whereas Team X beats them .796% of the time. NBA road teams beat Team X’s road opponents .348% of the time, whereas Team X beats them .262% of the time. Then Team X’s Relative Winning Percentage would be .518%. Calculation: (.123 – .086)/2 + .500).

RWP is meant to be a simple and reliable method of judging the objective strength of each team regardless of opponent or location. It splits each team’s home and away calculations and weights them evenly to favor teams with more balanced strength.

### The Movers this week

This week’s RWP Power Rankings are remarkably consistent with the rankings I did on January4th. Cleveland maintains the NBA’s highest RWP, with Boston supplanting Atlanta in the number two spot. The largest rise belongs to the Utah Jazz, which moved up five spots to number 8. The Sacramento Kings (18 to 22) and the Dallas Mavericks (8 to 12) tied for the largest drop.

One other note. When you consider the fact that somewhere around 29% of all games (about 24 games) are decided by luck rather than strength, and that a team ought to win half of those games, then the New Jersey Nets could be one of the worst teams in history. Its RWP of .126% would translate into 10 wins, less than the amount of wins a team should be able to fall ass backwards into (12). That’s monumentally bad.

Here are the results. I listed each team’s previous ranking in parenthesis.

### NBA POWER RANKING (by Relative Winning %)

1. Cleveland Cavaliers (1)____________________(.678%)

2. Boston Celtics (3)________________________(.676%)

3. Atlanta Hawks (2)_______________________(.666%)

4. Los Angeles Lakers (4)____________________(.657%)

5. Orlando Magic (5)_______________________(.653%)

6. San Antonio Spurs (6)____________________(.639%)

7. Denver Nuggets (7)______________________(.626%)

8. Utah Jazz (13)___________________________(.599%)

9. Oklahoma City Thunder (10)________________(.597%)

10. Portland Trailblazers (12)_________________(.590%)

11. Phoenix Suns (9)________________________(.586%)

12. Dallas Mavericks (8)______________________(.572%)

13. Houston Rockets (11)_____________________(.537%)

14. Miami Heat (14)_________________________(.521%)

15. Charlotte Bobcats (16)____________________(.510%)

16. Memphis Grizzlies (15)____________________(.504%)

17. Toronto Raptors (17)_____________________(.492%)

18. **Milwaukee Bucks** (19)___________________(.462%)

19. New Orleans Hornets (20)__________________(.441%)

20. New York Knicks (21)_____________________(.437%)

21. Los Angeles Clippers (22)__________________(.410%)

22. Sacramento Kings (18)____________________(.406%)

23. Chicago Bulls (27)_______________________(.405%)

24. Philadelphia 76ers (26)___________________(.403%)

25. Washington Wizards (25)_ ________________(.383%)

26. Detroit Pistons (23)_____________________(.373%)

27. Golden State Warriors (24)_______________(.368%)

28. Indiana Pacers (28)_____________________(.332%)

29. Minnesota Timberwolves (29)_____________(.215%)

30. New Jersey Nets (30)____________________(.164%)

Tags: Courtside Analyst, NBA Power Ranking, Relative Winning Percentage

February 5, 2010 at 1:06 pm |

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