For most of the best teams in college football, Week 8 didn't move the needle all that much. Georgia and Michigan were idle, Tennessee played UT Martin, Alabama worked methodically through its annual post-loss blowout of Mississippi State, and Ohio State dominated an offense-less Iowa.
There were plenty of thrilling games, of course, but nothing that affected too much at the top of the SP+ rankings. And of the current SP+ top 10, Clemson was the only team to see its ranking move by more than one spot. (That's a bit of a surprise considering Ole Miss is in the top 10 and got blown out by LSU. Strangely, while LSU's rating jumped quite a bit, the Rebels' stayed about the same.)
Below are this week's SP+ rankings. 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.