Ratings Percentage Index

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Commonly known as RPI, the Ratings Percentage Index is one of the rating systems whereby NCAA basketball teams are ranked. This system has been in use since 1981 to aid in selecting and seeding of the teams appearing in the 65-team men's playoffs (see also, March Madness). It has also been used to aid in the selection and seeding process for the 64-team women's tournament since its inception in 1982. The Index comprises that team's winning percentage (25%), its opponents' winning percentage (50%), and the winning percentage of those opponents' opponents (25%).

Some feel that this heavy emphasis upon strength of schedule unfairly advantages teams from major conferences. Teams from "majors" are allowed to pick many of their scheduled non-conference opponents (often, blatantly weaker teams); but, teams from "low-major" conferences may only get one, if any, such chosen-opponent "slot" on their schedules. On the other hand, some "mid-major" conferences compel their member-teams to regularly schedule opponents ranked in the top half of the RPI, which could eventually boost the strength of that conference and/or its tougher-scheduling teams. The Missouri Valley Conference has successfully done this: It has become one of the top-rated RPI conferences, despite having very few of its teams ranked in the two national Top 25 polls. [1] For the first time, in 2006, the NCAA decided to release their RPI calculations weekly starting in February. Independent sources, such as ESPN or CNN/SI, also publish their own RPI calculations, which are updated more frequently.

The RPI was updated in 2004 to account for differences in home and away games. A home win now counts as 0.6 win, while a road win counts as 1.4 wins. Conversely, a home loss equals 1.4 losses, while a road loss counts as 0.6 loss.