I was curious to see whether the passage of time has changed how the Tournament Committee makes its seeding decisions. Does an 0.60 RPI have the same meaning in 2018 as it did at the beginning of the 21st century? Do teams with an 0.60 in 2018 get about the same seeding as they would have received in 2000?

To address this question I simply added a term that measures the number of years since 2000 to my standard model. The effect is significant and uniform across all three types of conferences. This chart presents the estimated relationship between RPI and seeding for major conference teams setting the elapsed time variable to its extreme values of one (2001) and 17 (2017).

The difference is substantial. Since 2000, the Committee has reduced the seedings they grant by about 1.3 ranks.^{1} Another way to look at this is to ask how much greater does a team’s RPI need to be in 2017 to get the same seeding it would have gotten in 2001. In 2001, a six seed would have required an RPI of 0.602; in 2017, that floor had been raised to 0.613. In the RPI rankings for 2018, that small numerical difference in RPIs represents the gap between Arizona (0.612; 18th in RPI) and Loyola-Chicago (0.6027; 26th).

^{1}I calculate this effect by multiplying the estimated coefficient 0.0787 ranks/year by 17 years. Letting this effect vary by type of conference added no explanatory power (*p*>.75 no difference). A test of whether the slope of the relationship between RPI and seeding varied over time, by including the interaction of RPI and time, was similarly unproductive. The gap in seedings did not change over time producing the parallel lines in the graph above.