I think the average used to be in the 30's very recently but has surpassed 40. Seeing this, some applicants want to apply to 50. In a few years, the average will be 50, prompting people to apply to 60.
In 10 years, will the average number be 100?
Because of scheduling conflicts, one can probably only interview at 15, 20 at most.
I think that if you can't get many interviews, applying to more places won't generate many more interviews. Therefore, if you looked at people applying to 100 places, a number of them would get 50-80 interviews and a number of them would get 0-5 interviews but few would be in between.