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Preseason SP+ rankings: Alabama tops Clemson

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The numbers prove Alabama and Clemson's dominance (0:52)

It's hard to deny Alabama and Clemson's dominance, especially after crunching the numbers. (0:52)

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 intended to be predictive and forward-facing. That is important to remember. 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.

The SP+ rankings generally perform well against the spread -- 52 to 54 percent success over a full season, which is excellent for a system projecting every game and not specifically adjusting for injury.

What goes into the projections?

The offseason projections -- which, like ESPN Stats & Information's Football Power Index, carry diminishing weight in the SP+ formulas throughout the season -- are comprised of three factors:

Recent history: I use a weighted five-year history as a way of gauging program health. For most programs, what they have done of late is what they will most likely do moving forward.

Returning production: Instead of using returning starters, I created a formula for returning production based on which units seem to have the most effect on a team's improvement or regression. As it turns out, continuity at quarterback, receiver and the secondary is far more impactful on SP+ rating the next year than continuity in other units. Accordingly, turnover in those areas takes on heavier weight.

Recent recruiting: Returning production measures what a program lost, and a two-year recruiting average fills in the gaps on what kind of talent and athleticism it has acquired to replace the lost producers.

I attempted to account for as many offseason transfers, dismissals and injuries as possible in the below numbers. Here are the current 2019 ratings, presented in the form of an adjusted points per game figure. No. 1 Alabama's rating of 35.3 means the Crimson Tide are projected to be 35.3 points per game better than the average FBS team, while No. 130 UTEP's rating of minus-30.2 means the Miners are projected to be 30.2 points per game worse than average.

For a conference-by-conference breakdown, click here.