College Football By the Numbers
By the Numbers
Welcome to By the Numbers, a college football rating site. After a brief description of the rating system, you will find links to postings from 2000 to the present.
The rating system used is amazingly simple. I assign each team a "power rating" that can predict games well. If Clemson is rated at 114 and Auburn is rated at 107, that means that Clemson is 7 points better than Auburn (coincidentally, the margin of victory for the 2012 game). The home field advantage averages about 4 points, so my prediction would add or subtract 4 depending on where the game is played. Though the ratings are designed to predict games, they can also serve as a ranking system, since the higher the rating the better the team is.
The ratings come from a simple system that is a modification of what is now known as the Massey system. I only use the teams' schedules, points for and against for the season and net wins (wins minus losses) for the season. That's all. No adjustments for when the games were played, where the games were played, who was injured, or anything else. I find it surprising that such a simple system actually predicts future games well (about 75% winners and a little over 50% against the spread). As a bonus, the derived rankings match the polls to a large extent.
There are different aspects of the ratings that I publish (starting in 2013). The offensive rating measures how many points each team should score against an average defense. The defensive rating measures how many points the opponents would score on this defense compared to an average defense. The points rating is the sum of the offensive and defensive ratings. The wins rating, described below in more detail, is the version of the ratings that ignores points and only uses wins and losses (and schedule). BCS computer systems were required to ignore points. The overall rating is a weighted average of points and wins ratings, with slightly more emphasis on the wins ratings.
You should view this rating system, or any other rating system, as a piece of evidence that might be useful to your evaluation of the college football system. Since I am telling you how this system works, you can correct for all of the missing details. The following tell you how the teams stacked up ... by the numbers.2017-18