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 drop down eight spots to #19 this week after a dismal offensive performance against the Rams, who climb into the #11 spot the Seahawks vacated. The Chargers take over the top spot with the largest one-week gain in Team Strength (+7.5). It is unlikely you will see any other rankings with the Chargers at #1, but come back in a few weeks and tell me which ones turn out to be right. Having seen this team up close, their rank is not a surprise. Arizona is rightfully next-to-last, which scares the hell out of me with so many good QBs available in the draft next year.
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. Take a look at the cliff'o'doom at the zero mark. Washington and Seattle are on the razor's edge of dropping into the nether regions of the NFL. On the other end, you can see the top four teams starting to separate themselves from the pack.