Here I have developed a mathematical formula as a way as calculating a type of power ranking system for the NBA.  I have done this to create an unbiased power ranking system that is dictated by the statistics that tell us how successful a team has been and how they should continue to perform as time goes on.  Let me first tell you the factors that go into the formula and the ranking system.

The most important part of the power ranking formula is the Pythagorean Method.  This method predicts the expected winning percentage for a team based on the team’s offensive and defensive efficiency ratings.  A team’s won-loss record is obviously strongly related to how many points they score and how many they allow.  

Offensive and defensive efficiency ratins are the number of points scored or allowed per 100 possessions.  This is the best way to evaluate offenses and defenses, and much better than using the traditional points per game stats.  These efficency ratings take many things into account: shooting percentage, points scored, turnovers, offensive rebounds, and turnovers.  These efficiency ratings are then used in the calculation of the expected winning percentage as a result of the Pythagorean Method.  Here is the formula to calculate expected winning percentage:

Expected Winning %=(Off. Eff)^{^(16.5)}/[Off. Eff^{^(16.5)} + Def. Eff^{^(16.5)}]

The expected winning percentage accounts for half of the value of a team’s rating in these power rankings.  The other factors involved are a team’s actual winning percentage, winning percentage in the last ten games, and strength of schedule.  30% of a team’s rating is based on their winning percentage because it is important to tell what games teams are able to pull out and win.  Efficency ratings do not take into account consistency but a win-loss record gives us a better idea of that.  10% of the ratingis based on the win percentage over the last ten games to account for how a team is playing recently.  10% of the rating is also based on strength of schedule since it is important to factor in the quality of opponents that different teams have faced.

Overall, the formula for the NYKC Power Rating is:

Power Rating = (50 x Expected Winning %) + (30 x Actual Winning %) + (10 x Winning % L10) + (10 x SOS)

The NYKC Power Rating calculations will be done weekly and there will be a power ranking post showing us the results every Monday.  

Archive of NYKC Power Rankings:

NYKC Power Rankings: 12/29/08