The difference between a ranked and unranked waitlist are as follows. A ranked waitlist is ranked so that there is an order list of who will get in off the waitlist 1st, second, third, etc. This way the school can tell you you are number 4 on the waitlist meaning that 4 spots need to open up before you get in. Unranked waitlists do not have an order list. This way if a white male with a 3.5 GPA turns down his acceptance the school can pull another white male with about a 3.5 GPA off the waitlist and keep the class dynamics similar.