Pythagorean Wins for the NFL

This article has nothing to do with web development, search engines, or accessible design. But if you like betting on football, please read on.

Pythagorean wins are the number of games a team should win based on three factors:

• the number of games they've played
• the number points they've scored
• the number of points they've given up

A team's pythagorean win total is an excellent indicator of how good that team really is. I wrote a script that calculates pythagorean wins for NFL teams (Download PHP Source)

NFL coaches, Bill Parcells and Bill Belichick are often quoted as saying, "You are what your record says you are". I'm not going to argue with Belichick, but according to pythagorean wins, some teams are better than their record, while others are under-achievers or unlucky.

When two teams play each other, the winner is usually the team with the higher pythagorean win total even if the other team has a better win/loss record. According to Aaron Schatz of footballoutsiders.com, the team with the top Pythagorean record has won the Super Bowl 16 of the last 20 years.

Bill James, the sabermetrics guru from the baseball world is credited with formulating pythagorean wins. Square the number of points a team has scored and divide it by that same number plus the square of the number of points the team gave up.

The actual factor (the 'square') is a little different for different sports. For baseball, the factor is 1.83; for the NFL, the factor is 2.37; for NBA Basketball, the exponent is 13.91; for NHL Hockey...um, let's get back to football...

Exceptions
Some teams over-achieve, while others under-achieve. Hence, the cliche, "any given Sunday". Let's look at Green Bay (under-achiever/unlucky) and New England (over-achiever/lucky):

Green Bay's winning percent is 55.2% - based on the number of points they've scored and allowed. (201^2.37 / (201^2.37 + 184^2.37)). They should win more than half the games they play. Yet at week 10 in the season, the Packers are 2-7. New England has a winning percentage of 41.2% - they should be a sub-.500 team, yet they're currently leading the AFC East at 5-4.

Green Bay and the Pats are actually exceptions to the rule. Check out the script for all the other NFL teams (updated weekly).

Resources

• My own script that calculates NFL Pythagorean Wins each week
  Download the PHP Scripts
• Boston Globe article about Aaron Schatz, FootballOutsiders.com, and Pythagorean Wins
• Baseball Prospectus article about Bill James and Pythagorean Wins
• Pythagoras on the Gridiron at FootballOutsiders.com