July 21, 2009


Proposal for Changes in Computing RPI - Part 2


Greg Van Zant, the head coach at West Virginia University, recently sent the following recommendation to the NCAA Division I Baseball Committee to change the formula for calculating the Ratings Percentage Index (RPI).



The Weighting of the Three RPI Factors


As you are aware, the RPI formula consists of three factors:

  1.   Division I winning percentage

  2.   Opponents average winning percentage

  3.   Your Opponents, Opponents winning percentage


Originally in 1984, the formula was 20-40-40 and in 1994 was tweaked to the current 25-50-25 for factors 1, 2 and 3.  One of the reasons for reducing Factor 3 from 40 to 25 was that mathematicians confirmed that too much weight placed on Factor 3 gave weaker teams in strong conferences an inflated RPI while penalizing strong teams in weaker leagues for having to play the teams in their league each season.


Many coaches and others in the baseball community are convinced that the current RPI formula over-rewards average teams in strong conferences and excessively hurts strong teams in weaker conferences.  This is because 75% of the current RPI is based on who you play and only 25% is based on your success.  Teams control their own success but have only limited control of their schedule.  21 to 30 games a year are dictated by conference affiliation and most of the non-conference opponents are based on where a school is geographically located. 


It is very unfair that some teams currently have a built in advantage every year with the RPI due to their conference affiliation or geographical location.


Major League Baseball uses the RPI weighting of 100-0-0 to rank their teams even though they play unbalanced schedules.  As you know, MLB teams in weaker divisions have an easier schedule than teams in tougher divisions.  However, MLB bases standings strictly on winning percentage and they do not factor in strength of schedule at all.


The variance in schedule strength is greater for college baseball teams than for MLB teams, so taking into account strength of schedule to adjust winning percentage makes sense for college baseball.  But it doesn't make sense that winning/success is only worth 25% of a team's ranking and who you play is worth the other 75%, especially when you can't control most of who you play.


All the RPI does is take a team's win-loss percentage and adjust it up or down, based on whether the team played a strong or weak schedule.  A team's winning percentage and success should be worth at least half of their ranking.  The other half should be their schedule strength.  With 50% of the RPI based on winning percentage and 50% based on the strength of the schedule, one could expect to see results like this.


Team A  #1 winning percentage and #1 strength of schedule = #1 ranked team

Team B  #1 winning percentage and #302 strength of schedule = #151 ranked team

Team C  #302 winning percentage and #1 strength of schedule = #151 ranked team

Team D  #302 winning percentage and #302  strength of schedule = #302 ranked team


A 50-35-15 breakdown for the RPI factors would mean that the first 50% of a team's RPI would be their own winning percentage, which is the most important factor for any team and it is what they can control.  The second factor, the opponents winning percentage (35%) and the third factor, the opponents, opponents winning percentage (15%) would be the remaining 50% of the RPI which measures schedule strength.  Opponents, Opponents winning percentage is the least important and the least controllable of the three factors and thus should be the least weighted factor.


With the current 25-50-25 formula, something as far out there and uncontrollable as your opponents, opponents winning percentage is equally important as your own team's winning percentage. 


It can be argued that all 12 teams in the top conference are better than all of the other top teams from every other conference.  It can also be argued that they aren't better.  The current 25-50-25 gives a team that finishes with a losing record in a strong conference too much of a bump up in the RPI.  The current RPI formula can rank a team very high that lost all year long in its own conference.  This team may be strong, but they had all year to beat the top teams in their own league and they couldn't do it.  We need to adjust this RPI formula so that teams that have success in other conferences can have a chance in the post-season to do what those bottom teams in top conferences tried to do all year and couldn't.


How about Team A who plays its natural rival and closest Division I opponent, Team R, four mid-week games each year due to academics, economics and common sense.  In year one, Team R has a win-loss record of 30-25 and the next year Team R is 15-40.  Team R's influence on Team A's RPI is going to be much more positive in year one than in year two.


Assuming that Team A had identical teams in years one and two, and everything else was equal, Team A would be ranked higher in the RPI in year one.  Does the fact that Team R had a bad year mean that Team A is a weaker team?  Should the strength of another team, which you have no control over, determine your ranking?  This is a big reason that the total percentage of the RPI dedicated to strength of schedule should be reduced from 75% of the RPI (25-50-25) to 50% of the RPI (50-35-15).


We need to reward success more, just like the ABCA does with the All-America Team nominations and selections.   The ABCA emphasizes that the All-America Teams are to recognize success instead of pro potential.  We need to reward Division I teams more for the success they have and less for what conference they are in, where they are located or their perceived strength due to an over-inflated RPI.  Winning and strength of schedule are both important factors when ranking teams and they should both be considered equally.


Various simulations of the RPI using different formulas have resulted in some significant differences in team rankings.  Some teams have moved up as many as 44 spots while others have dropped as much as 42 spots.  If those two teams were ranked equally before a certain manipulation of the RPI, they could be ranked 86 teams apart with a new RPI formula.  This is the difference between playing in the post-season and staying home.

Part 1 - Overview


Part 3 - The Weighting of Home Wins and Road Wins


Part 4 - Exempt Contests vs. Non-Division I Teams; Bonus & Penalty System


(photo by Jimmy Jones)