Power rankings are always debatable. I don’t buy into the gut feel methods most places use to determine their rankings, so I developed a formula a few years back that attempts to take at least some of the subjectivity out of the discussion. My approach is simple, I measure offensive and defensive efficiency based on the Yards Per Carry (YPC) and Yards Per Attempt (YPA), as well as points scored and points allowed. The formula to calculate “Team Strength” is as follows:

(YPC (offense) + YPA (offense) + Avg Pts/Game Scored) – (YPC (defense) + YPA (defense)+ Avg Pts/Game Allowed)

The formula has proven to be a pretty accurate predictor of success. Even in the first week of the 2008 season, 5 of the top 10 ranked teams were playoff bound. As with any statistic, it becomes more meaningful as the sample size grows. Usually, these become most meaningful after Week 3. In 2007, 9 of the top 10 ranked teams were playoff teams, with the lowest ranked playoff team coming in at #15. In 2008, 8 the top 10 were playoff teams, with Arizona being the lowest ranked playoff team at #19. I’m not sure any formula could have predicted their run.

If you’d like to see how teams rankings changed from 2008 to 2009, you can read more here.

The Seahawks remain steady at #11 this week despite giving up a ton of yards. The rankings formula accounts for games like that since absolute scoring differential is a much larger factor. Mike Vick and the Eagles made the largest climb, gaining 10.3 of their 10.8 Team Strength. We are through week 3, so these rankings start to take on real meaning. It’s likely 70-80% of the Top 10 will make the playoffs, based on history.

Scatter chart of the rankings. This view helps to give you a view of how teams are grouped together. You will generally see tiers of strength develop as the season wears on. Note the bunching between 5-12, and the dropoff down to 2 and lower.

2 Responses

  1. Anonymous

    I applaud your effort, however I question how well it really works. You mentioned that you correctly predicted 70 to 80% of playoff teams after week 3, but did you have the Division winners ranked higher than the wild card teams? Because it is so heavily weighted by scores, wild card teams that beat the crap out of the dregs of the league and lose every close game to the better teams in the league could still be ranked higher than a team that relies mostly on defense like the Ravens or Titans and wins games 17 to 13 instead of 30 to 20. I definitely think you're formula will separate the worst teams out, but I have a hard time believing it can tell the difference between the better teams.

  2. hawkblogger

    Thanks, Mark. I believe every ranking formula is flawed, but this one has proven to be an early predictor of which teams matter and which do not. I spent time tweaking the algorithm with more advanced statistics, but greater complexity does not always yield greater accuracy. I think you'll find these rankings will prove to be as valuable as any out there.