In the 2015-2016 CWRU CDS, I see
Offered place on wait list:9,446
Number accepting place on wait list: 5,119
Accepted from list: 518
So 10% get off the waitlist.
https://case.edu/ir/media/caseedu/institutional-research/documents/common-data-set/2015-2016-CDS.pdf
Case will ask you if you want to be on the wait list. Obviously say yes.
You may get a mail like:
Hi
Thanks for letting us know of your continued interest. We will provide more information on the waitlist in the coming weeks. Please be sure to respond to the email asking you to confirm your interest in the waitlist.
Feel free to write us back with further questions, or call 216.368.4450 Monday-Friday, 8:30 a.m.-5 p.m., to speak to an admission counselor.
Then you may get an email like:
"As we enter the final weekend before the National Candidate’s Reply Deadline of May 1, we have closely monitored the responses to our initial offers of admission and it appears that we will have a limited number of places available to admit students from the wait list. I am contacting you because you have indicated your interest in Case Western Reserve, and we would like to be able to consider your candidacy for the Class of 20XX.
If you are offered admission, you will also be offered a scholarship of $XX,000 per year. If you qualify for additional financial aid, we have also prepared a preliminary financial aid award for you, which you can view by logging into our financial aid portal at http://financialaid.case.edu/myfinancialaid.aspx. You will need your activated CWRU Network ID to login. Instructions on activating your ID are below.
Once you have reviewed this information, (and your financial aid, if applicable,) you will need to get in touch with us as soon as possible at admission@case.edu or 216.368.4450. Admission counselors will be answering the phone between 9 AM and 5 PM EST on Saturday and Sunday, and responding to email throughout the weekend.
The admission committee will also be meeting throughout the weekend, and we want to be able to extend offers of admission as quickly as possible to students like you who are most interested in becoming part of the Case Western Reserve community. Please be in touch with us as quickly as possible to let us know of your interest and with any questions you may have.
Once again, if you are interested in being admitted from the wait list and your scholarship and aid package makes it possible for you to attend, it is imperative that you respond to this email right away with an indication of your level of interest."
http://talk.collegeconfidential.com/case-western-reserve-university/1644476-possible-admission-from-waitlist-email.html
So they would only admit you if you would 100% attend, because at the waitlist point they want the admissions=enrollment.