The Gini coefficient is a 0-to-1 statistical measure of divergence that's normally used to describe income inequality in a country. In a nation with a Gini coefficient of 0, everyone would make the same amount of money while a nation with a coefficient of 1 would be purely unequal.
The Patriots have a Gini coefficient of 0.51, just a touch under the woeful Tennessee Titans — which only won three games in the 2015 regular season — at 0.52. The closer that figure is to 0, the more equal the payroll distribution.
There are some interesting patterns in the data. The New York Giants, for instance, have an Gini coefficient of 0.56, putting them solidly in the most equal quarter of the league. That's despite the fact that Super Bowl winning quarterback Eli Manning makes an average of $21 million a year, ranking him the fourth-highest-paid player in the league. His pay makes up 16 percent of the Giants' salary cap, and it's been reported that he wants even more.
The Patriots' low Gini coefficient is partly due to quarterback Tom Brady's (comparatively) modest contract. His $9 million annual average salary is far less than many star quarterbacks, like the Green Bay Packers' Aaron Rodgers ($22 million), the Seattle Seahawks' Russell Wilson ($21.9 million), the Pittsburgh Steelers' Ben Roethlisberger ($21.85 million) and the Carolina Panthers' Cam Newton ($20.8 million). The only Patriot that makes more than $10 million, on average, is offensive tackle Nate Solder — who hasn't actually played since tearing his bicep in a game against Dallas in October.
Read MoreNFL's St. Louis Rams approved to relocate to Los Angeles
Brady renegotiated his contract in 2013, and agreed to terms that lowered his average annual take home pay. That gave the team more space in its salary cap. As some observers have pointed out, it's not entirely altruism on Brady's part: He took a $30 million "signing bonus" in addition to the lower yearly salaries going forward.
The $9 million average annual salary that Brady is taking home now is for the first "out year" in which Brady has no guarantee. However, it's unlikely the Patriots would want to drop him considering how well he's been playing.
Still, that puts Brady in the lower half in terms of starting quarterback pay. That's especially surprising when you consider that he has four Super Bowl rings and finished the season fourth in quarterback ratings.