Don's answer is technically correct because the original poster (OP) did not specially ask about the MFE program at UMich. That said, it is often understood that many programs discussed here are MFE without mentioning specifically.
More to the question, the waitlist is used as a safe vehicle for programs to make sure they can fill their quota.
This is very clear if we take a second to look at programs like UCB MFE that admits 65 students a year. They are well known for having many people on a waitlist. See UCB MFE wiki
At the other end, I'm pretty certain Baruch MFE does not have a waitlist as they admit vastly differently number of students each year. See Baruch MFE wiki
And in the middle, you have other programs with unofficial quota, soft quota, hard quota, flexible quota which employ the waitlist strategy as a safe bet.
To answer your question, we need to know the size of the waitlist, the quota, the yield rate of previous years.
It would be funny to turn around and put programs that you got admit into your wait list and ask them to wait for your decision.
yes,I mean the MFE program in UMich. Besides waiting, what else can I do to make up for the admission? Clearly I don't know how much I rank in the wait list. Does the dean write the same word to applicants who are put in the wait list?
There isn't much you can do about it except by getting admission at B where B is a better than A and then informing A about this. This may give you some competitive edge over waitlist fellows.
Don't quote me on this but knowing how each program has different criteria, it's entirely possible to get rejected or waitlisted at A and admit at B where B > A.