As a comparison, the 50th best 3-pt shooting team last year (Quinnipiac) shot 35.7%. The year before, with the line closer, the 50th best (Nicholls St.) shot 37.0%. Last year, 4 teams shot better than 39%, 11 did it the year before. Moving back the line also lowered overall percentages. KenPom or somebody said it also seemed to affect mediocre shooters more than good ones, which makes sense.
Math nerds will point out that lowering the percentage even one point is significant for 3 pt baskets in a philosophy of only taking 3s and layups. It moves the needle slightly in calculating the value of 10-foot jump shot vs. a 3 pointer. Villanova seems to be a trend setter in getting into the lane, jump stopping and using these short, high-percentage jump shots. If you can shoot 60% on them, then it's as efficient as a 40% 3 pt shot. Of course, an 18 foot jump shot is still a bad shot.
Sorry if anybody gets a headache from this post.