If anyone is interested in waitlist stats for the last 4 years, these are from the common datasets:
of applicants offered Waitlist vs # of applicants accepted off Waitlist::
2017: 3168 offered waitlist and 15 accepted
2016: 1011 offered waitlist and 675 accepted
2015: 1888 offered waitlist and 134 accepted
2014: 1598 offered waitlist and 67 accepted