Can you name the most dominant team of the past four seasons?
Some fans would say the reigning Super Bowl champion New England Patriots. The Patriots certainly have won a lot of games -- and they're the dominant team if we're talking about ESPN headlines. Other fans would say the Denver Broncos, who have the best regular-season record (50-14) since signing Peyton Manning to play quarterback. But the Broncos haven't had the playoff success that would mark them as the dominant team of this decade.
One team has clearly dominated the NFL over the past four years if we analyze every play of every game, and that team is the Seattle Seahawks. Football Outsiders' DVOA ratings analyze every single play, comparing success on that play to a league-average baseline adjusted for situation and opponent. Because they combined huge wins with close losses, the Seahawks finished No. 1 in DVOA this year despite going only 10-6. The Seahawks also finished No. 1 in DVOA the year before, when they were 12-4. And they were No. 1 in 2013 when they were 13-3 and won the Super Bowl. And they were even No. 1 in 2012 when they started their current playoff run with an 11-5 wild-card season.
That's right: We've had Seattle at No. 1 for four straight years. DVOA ratings currently go back to 1989, and no other team has matched the 2012-2015 Seahawks. The only other teams to finish No. 1 in consecutive years were the Dallas Cowboys in 1992-1994 and the Green Bay Packers in 1996-1997.
Which other teams have been consistently good and bad over this four-year period of Seahawks ascendency? To answer that question, we've looked at DVOA ratings from the past four years, combining both the regular season and the playoffs. Each postseason game is given twice as much weight as a regular-season game. We didn't want to penalize teams for getting a top-two seed or reward bad teams for missing the playoffs, so each top-two seed is treated as if it won a wild-card game with the average rating of wild-card winners, and each team that missed the playoffs is treated as if it lost a wild-card game with the average rating of wild-card losers.
Instead of averaging the four ratings, we used a mathematical concept called harmonic mean, which emphasizes consistency; teams with four good years will have a higher harmonic mean than teams with two great years and two bad years.