ABOUT THE CPI
The CPI (Comparative Performance Index) reflects the strength of
team performance during
a season by balancing a team's record with those of its
opponents, independent of the team. The formula is designed to be clear
and intuitive, with accurate, sensible results.
Similar to the NCAA's RPI, teams are rated using only
the win percentages of themselves and their opponents. The
formula rates each team according to the following:
[ CPI Rating =
where W% is the team's win percentage,
Ow% is the team's opponents' win percentage
independent of the team, and
Oow% is the team's opponents' opponents win percentage
independent of the team's opponents.
All percentages are taken as the sum of wins over the sum of
games played. The design gives greater importance to games
closer to a team's circle of competition, balances a team's
record equally with its schedule, is unbiased, and makes no
To account for non-FBS competition, the final rating is the greater of two
calculations, one which includes all games played, including FCS opponents and
opponents' opponents, and one which ignores
results of games between FCS level competition. This eliminates
negative distortion from results outside of FBS competition. FCS ratings
also exclude results of
games outside of FCS competition.
The results are strongly aligned with polls of college football
experts and more complex computer algorithms.
By compounding the win percentages
through multiplication, the CPI creates a more accurate rating while maintaining the common sense intuition of
a formula like the
Ratings and percentages from past years can also be compared in a consistent way with
today's top teams, for insight into the shape of the
college football landscape and the quality of title
Importantly, the system is transparent. Ratings are listed
with wins and losses, win percentages, and the team's strength
of schedule ranking. Readers can see exactly how
each team is ranked on the basis of their record, and can judge
the legitimacy of each ranking. The ratings are also
verifiable through the CPI's open formula.
The CPI has correctly matched the top two teams for the BCS
title game in eleven of fourteen years, putting it on par with
individual BCS computers in aligning with the BCS standings and opinion
polls for the title matchup. The CPI also aligns well with the 25-team BCS Standings
throughout a given season.
The CPI does not take into account margin of victory, location,
or any measure other than win percentage in its calculation.