I thought this was an interesting theory - that it's not so much that teams are becoming more efficient but that the top is becoming stronger, the middle weaker, and thus the top appears more efficient relative to the middle.
So, I looked into it a little more. I looked at points per possession for every cbb team since the 97-98 season. What you'll see below is the median, the average of the top 10 teams and the average of the bottom 10 teams. Additionally, I've indicated when NET took effect as well as immediate transfer eligibility. Finally, just for reference, I've also added the Google search volume for "kenpom" since 2004.
My takeaways are:
A) You're right that the top is more efficient this year relative to the median. It's the largest disparity between the top teams and the median since the data starts in 1998. (It's almost exactly the same as it was in 1998.)
B) There is a clear upward trend in points per possession (a measure of efficiency) for all levels of teams
C) There is a clear spike in PPP that started in 2023 (unsure of the significance of that year)
D) There does seem to be a correlation between increased Kenpom popularity and the recent increase in efficiency
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KenPom Google volume (the spikes happen each March)
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