At long last, the RPI is on its way out as a meaningful NCAA tournament-related metric.
The NCAA announced on Wednesday the creation of a new ranking system that will replace the notoriously flawed Ratings Percentage Index as the “primary sorting tool for evaluating teams during the Division I men’s basketball season.”
The new index has been dubbed the NCAA Evaluation Tool, or NET for short. An NCAA release said it “relies on game results, strength of schedule, game location, scoring margin, net offensive and defensive efficiency, and the quality of wins and losses.”
How does the NET differ from the RPI?
The RPI was based solely on winning percentage, opponent winning percentage, and opponents’ opponent winning percentage – and far too heavily on the latter two categories. It lacked theoretical or statistical nuance. Many schools had cracked the code and figured out how to game it.
The NET will look beyond win/loss records, breaking every game down by possession, and factoring in where the game was played. It will value a blowout on the road more than a narrow escape at home.
The NCAA did specify, though, that “a cap of 10 points was applied to the winning margin to prevent rankings from encouraging unsportsmanlike play, such as needlessly running up the score in a game where the outcome was certain.”
The 10-point cap seems far too low, considering that final margins often depend heavily on late-game fouling. Under the cap, there’ll be very little difference between a 30-point blowout and a one-possession game turned into an eight-point win by a final-minute free throw contest.
But overall, the NET is an improvement on the RPI.
The second straight year of NCAA tournament selection change
Last year, the NCAA instituted its quadrant system in an attempt to tier opponents and wins by quality and location. But it, too, was flawed, because it didn’t lessen the weight of the RPI. As Yahoo Sports’ Jeff Eisenberg wrote at the time:
While the quadrant system is a notable step forward, the flaw in it is that the team sheets are still dependent on the primitive, outdated RPI to determine what a quality win is.
Three-quarters of a team’s RPI score is determined by its strength of schedule, which makes who you play often more important than whether you win or lose. The RPI also doesn’t take into account margin of victory or defeat, meaning that a one-point win over a quality opponent is weighted exactly the same as a 30-point win over a quality opponent even though context clearly is relevant.
The NCAA, after meeting with analytics gurus and other experts in various fields, has decided to correct that flaw.
What is the main argument against NET?
The most rational qualm with the NET formula is the incorporation of predictive metrics such as offensive and defensive efficiency. They are useful for evaluating a team’s true quality.
But sport, as long as it has existed, has been based on results – wins and losses. The NET will help the committee judge who the better teams are. But better doesn’t necessarily equate to most deserving, and many believe tournament selection should remain a reflection of which teams have earned bids/seeds by winning games, not by playing good basketball.
There’s a difference. When you consider the contrast between a .500 team with 15 blowout wins and 15 one-point losses and another with 20 one-point wins and 10 blowout losses, you realize as much.
How would the NET consider those two squads if they played identical schedules? We don’t know the answer to that question, and it sounds like the NCAA doesn’t even know either …
Just spoke w/ Dan Gavitt. Some things to know:
—NET algorithm powered by artificial intelligence, thus isn’t something that’s “readable”
—NCAA owns NET metric
—NET will start w/ weekly unveilings in late-Nov/early Dec
—NCAA won’t apply NET metric to previous yrs for comparison
— Matt Norlander (@MattNorlander) August 22, 2018
The lack of transparency, and of a legible, easy-to-understand formula, is somewhat troubling.
Then again, the committee isn’t beholden to the NET rankings. Just because one team is higher than a rival doesn’t mean it must be selected ahead of that rival.
How important will the NET be?
The NET won’t be the end-all, be-all for the selection committee. No single metric is. In the end, the committee’s job is still a subjective one, as much as some want it to be otherwise.
So the NET, in theory, will be just as important as the RPI was. The NCAA calls it a “sorting tool.” It will have plenty of implicit power as committee members consider what constitutes a quality win and what doesn’t. It’s unclear how much sway it will hold beyond that.
Nonetheless, it certainly seems like a step in the right direction.
Is the RPI gone forever?
Nope. The RPI will still be used by the women’s basketball NCAA tournament selection committee, and by other collegiate sports. The NET only applies to men’s Division I basketball. But, presumably, its effective implementation could lead to similar metrics being introduced elsewhere.
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