The NFL has prided itself on parity over the past 20 years, but five teams remain undefeated through six weeks.

The Green Bay Packers, the Denver Broncos and the Cincinnati Bengals are 6-0, while the New England Patriots and the Carolina Panthers are 5-0. 

The Panthers have reached the playoffs in each of the past two seasons, while the Broncos and Bengals are on four straight seasons in the playoffs and the Packers and Patriots have made the playoffs in six straight seasons.

Before 2015, there had been only one season in which even four teams emerged with perfect records through six weeks.