I know that chances are “slim” and Harvard does not officially release waitlist stats. But any success stories and/or ideas? Also post if you’re waitlisted like me, would love to meet you haha 
https://college.harvard.edu/admissions/admissions-statistics
This link indicates that for the class of 2018, 30 students total were admitted off the waitlist. I’ve heard numbers of the size of the waitlist everywhere from 1,000 to 3,000.
I’ve also read that there have been years when no one was taken from the waitlist, and going back some years, there were years when significantly more than 30 were admitted off the waitlist.