How Many Teams Have a Chance

BillC over at S&P+ shows us the data over the last 40 years, form 1968 to 2018 - how many teams are good enough to be in the playoff, and then from that group how many are really title contenders.

What's the right number of playoff teams 4, 8, 12, 16?

On average, there are 7 playoff-caliber teams and 3 title-contender teams in any given year:

Current S&P+ top 10 (ratings and percentiles in parentheses):
1.Alabama (plus-35.7 adjusted points per game, 99.2 percentile)
2.Ohio State (plus-31.7, 98.4)
3.Georgia (plus-30.2, 97.9)
4.Clemson (plus-29.2, 97.5)
5.Mississippi State (plus-28.9, 97.4)
6.Oklahoma State (plus-25.5, 95.6)
7.Washington (plus-24.4, 94.8)
8.Penn State (plus-24.2, 94.7)
9.Oklahoma (plus-23.6, 94.2)
10.Michigan (plus-21.2, 92.0)

The best teams here will likely remain national contenders throughout the rest of the regular season.
•According to S&P+, Alabama has only one remaining game with a worse than 85 percent win probability (70 percent against Mississippi State on November 10) and is projected to lose, on average, just 0.9 games the rest of the way.
•Ohio State has only one remaining game with a worse than 77 percent win probability (61 percent at Penn State on September 29). The Buckeyes are projected to lose just 1.2 games on average.
•Georgia has no remaining games with a worse than 76 percent win probability. The closest the Dawgs come now are games with 76 percent (at LSU on October 13), 77 percent (at Kentucky on November 3) and 78 percent (at home vs. Auburn on November 10). That adds up to just 1.3 losses on average.
•Clemson, the shakiest team of the four thus far, has the cleanest remaining slate. The Tigers have only one remaining game with a less than 87 percent win probability: 70 percent at surging Boston College on November 10.