We relaunched our NFL Elo power ratings on Thursday with a nifty interactive that lets you track where your team stands and how likely it is to win each game. But Elo isn’t the only statistical power rating out there; in fact, our NFL previews used predictions and rankings generated by ESPN’s new Football Power Index (FPI), a system of far greater complexity. Since we plan to use both metrics in our NFL coverage throughout the season, we thought it would be interesting to look at how closely the two ratings mirror each other, as well as which teams fare better in each. (Note: To make an apples-to-apples comparison, I converted FPI to the same scale as Elo. I also updated the Elo-equivalent FPI ratings of New England and Pittsburgh to reflect Thursday night’s season-opening game.)
For the most part, Elo and FPI agree about the landscape of the league; the correlation coefficient between the two metrics is 0.94. But the fit isn’t perfect.
Elo thinks more highly of 17 teams — including the San Francisco 49ers, Oakland Raiders, Detroit Lions, Seattle Seahawks and San Diego Chargers — than FPI does. Among the teams that FPI favors, on the other hand, are the Indianapolis Colts, New Orleans Saints, Green Bay Packers, Miami Dolphins and Atlanta Falcons.
It’s tough to pinpoint exactly why the discrepancies exist in many cases (so many factors go into the FPI’s construction, in particular), but they’re worth keeping an eye on as the season progresses.
While Elo simply takes last year’s overall end-of-season ratings and regresses them to the mean, FPI adds some intricacies: It breaks a team’s quality down into components that measure its offense, defense and special teams, incorporates Vegas expectations, and employs subjective survey data from NFL experts.
While Elo simply takes last year’s overall end-of-season ratings and regresses them to the mean, FPI adds some intricacies: It breaks a team’s quality down into components that measure its offense, defense and special teams, incorporates Vegas expectations, and employs subjective survey data from NFL experts.
Probably because Elo has no idea they lost so much talent during the offseason.
While Elo simply takes last year’s overall end-of-season ratings and regresses them to the mean, FPI adds some intricacies: It breaks a team’s quality down into components that measure its offense, defense and special teams, incorporates Vegas expectations, and employs subjective survey data from NFL experts.
Probably because Elo has no idea they lost so much talent during the offseason.
Thus continuing Elo’s ongoing crush on the Seahawks.