You probably won't be shocked to learn this, but Georgia, the team that assumed the No. 1 ranking in SP+ nearly three months ago and just won the CFP National Championship by 58 points, has finished the season as the No. 1 team in the country, per SP+. The Bulldogs ended up with a 37.3 rating -- meaning they were regarded as 37.3 adjusted points per game better than the average college football team; their rating rose by 1.3 points after their shellacking of TCU on Monday night, while TCU's rating fell by 3.3 points. The Horned Frogs wrap up a dream season ranked eighth overall.
Below are the year-end SP+ ratings. What is SP+? In a single sentence, it's a tempo- and opponent-adjusted measure of college football efficiency. I created the system at Football Outsiders in 2008, and as my experience with both college football and its stats has grown, I have made quite a few tweaks to the system.
SP+ is indeed intended to be predictive and forward-facing. It is not a résumé ranking that gives credit for big wins or particularly brave scheduling -- no good predictive system is. It is simply a measure of the most sustainable and predictable aspects of football. If you're lucky or unimpressive in a win, your rating will probably fall. If you're strong and unlucky in a loss, it will probably rise.