Percentage of Shots Hit Below The Shoulder


Hall of Fame
I am looking for any study pertaining to how many balls in 3.0, 3.5, 4.0 play where the ball is below the shoulder of the net player, as he is hitting the ball, while he (the net player) is playing from inside the service box to the net.
This is not a bet, This is for a written study.
Comments welcome.