Okay, if you're just joining us for the final part in this series, you can read the first two posts (and everything else related to my ranking system, "Crunching The Numbers") through this hub. They cover a lot of background that I'll touch up on here, but the previous posts have a more in-depth analysis that I recommend you look at if you're a stat nerd like I am.
When I began my project of tracking and trending NFL statistics in 2013, it was only for the purpose of analyzing the metrics I used for Crunching The Numbers.