The Ratings Performance Index, commonly referred to simply as RPI, is a mathematical statistical formula that the NCAA has used since 1981 to evaluate and rank men’s college basketball teams.
It was implemented in 1984 as the method used to rank NCAA women’s teams. This system is based upon three factors. The first factor is a team’s Division I winning percentage, which accounts for 25 percent of the rating — games against non-Division I teams are not counted.
The second factor, which accounts for 50 percent of the RPI rating, is the winning percentage that their opponents have against Division I teams.
Finally, the third factor takes into account the team’s opponents’ opponents’ winning percentage versus Division I teams. That third factor makes up 25 percent of the RPI rating.
Well, now that you understand how the Ratings Performance Index works, you can throw all of that new-found knowledge out the window as it is no longer relevant in NCAA basketball.
The RPI system has officially been replaced with the NET model. NET, or NCAA Evaluation Tool, was approved in July as the NCAA’s new official system of ranking teams. It was tweaked during a trial period in the latter stages of the 2017-18 season and in the annual NCAA tournament.
How Is NET Different?
As opposed to using the factors that make up the old RPI system, the NET model takes into account the game results, strength of schedule, game location, scoring margins, and net offensive and defensive efficiency.
It also factors in the quality of a team’s wins and losses. In other words, the new NET system relies on many more factors which, in theory, should make it a more precise gauge to measure and rank NCAA basketball teams.
Another difference is that the NET omits such factors as game dates and the order in which games are played. This is supposed to balance out the importance of the early-season matchups with the late-season games.
Winning margins are also capped by 10 points which affects lop-sided victories. Overtime games will see the winning and losing margins set at 1 and -1 respectively regardless of the final score.
NCAA Basketball’s senior vice president, Dan Gavitt claims that the NET method is a “contemporary method” of analyzing teams by using metrics that are based on results. He acknowledges the fact that there is no such thing as a perfect ranking system but that the NET system will produce rankings that are founded on “an objective source of truth.”
Is NET Better Than RPI?
It’s difficult to say with any certainty whether the new system is better than RPI, although plenty of people believe that it is. One thing’s for sure though and that is the fact that there has been a demand for changes in the ranking system for a long time. Many critics of RPI call the method “flawed” and, on the surface, the NET appears to be a much fairer model and it is also predictive.
A ranking system that uses many more predictive metrics may have been an even more accurate system but the NCAA would have been in a bind as they don’t own or control those metrics and they would have been forced to outsource.
This new NET system has been put in place to make seeding and tournament selections a lot fairer and the early consensus says that the system is better.
Will NET Change The Tournament Landscape?
Changing from the RPI model to the NET system is bound to have a bit of an impact on tournament seedings. However, it is very unlikely that it will turn things upside down.
An example would be Wichita State who have done well in terms of advanced metrics only to fall victim to RPI and the selection committee. The new ratings system will benefit an efficient team like WSU who could see more favorable seeding. Of, course, for every team that gains, there will be teams that fall.
Still, the NET system should improve the tournament by being that much more precise in determining the seeds. It’s not as if undeserving and bad teams are going to suddenly start getting in.
