About half of colleges use a wait list, particularly those that accept fewer than half of all applications. Since students on average tend to be sending out more applications, colleges have been having a tougher time knowing for certain whether the students to whom they have offered admission will, in fact, attend in the fall. Some of the uncertainty is related to the phenomenon of students applying to more and more schools, sometimes 15 or more, to increase their chances in a statistical sense, but this adds a new layer of guesswork for colleges trying to predict how many accepted students will say yes, and puts waitlisted students in "limbo" or the "basic equivalent of purgatory," according to US News. In addition, many colleges lose some students due to a phenomenon sometimes called summer melt, meaning that some students, even ones who have sent in a deposit, will not show up in the fall, and melt away, and this "melt percentage" can be as high as 5% to 10% of persons who have paid a deposit.
The admission process is a complicated dance of supply and demand for colleges. And this spring, many institutions have accepted fewer applicants, and placed more on waiting lists, until it becomes clear over the next few weeks how many spots remain.
-- Jacques Steinberg in The New York Times, April 2010
As a result, colleges use wait lists as a hedge to make sure they have enough students in the fall. Some schools "under-invite" applicants in the regular admissions season to appear highly selective and then about-face and accept them from their wait lists later. One report is that Vanderbilt gets a tenth of their freshman class from the wait list. But it varies from college to college and from year to year. For example, in 2010 Stanford and Yale wait-listed 1,000 students while Duke wait-listed 3,000 students. Overall, one survey suggested that 30% of wait-listed students are eventually accepted, but this is an average figure for all wait-listed students, and the percentage is dramatically lower at elite or prestigious schools. There is a report suggesting that in recent years, the lists are more fluid than in previous years, in the sense that there is more wait list activity--which have become more of a safety net for colleges rather than students. Estimates vary about how many college applicants find themselves on a wait list; one report was that 10% of applicants were wait-listed.
One adviser suggested that students who are wait-listed "work the wait list" by staying in touch with the admissions office to make sure they know the student will attend if accepted, and possibly take steps such as forwarding new grades and making a subsequent college visit, or send a one-page letter or 60-second video describing a strong desire to attend and the reasons. A former dean of admissions at Franklin and Marshall College suggests that students not view the wait list letter as a "polite denial" but rather as a possible opportunity. A second report in 2011 confirmed this, and it suggested that private colleges without "billion-dollar endowments or 40,000 applicants" were finding that the period from May to the start of classes in fall was a time of uncertainty, with many institutions seeking new applicants, and unsure how many of the applicants that had promised to attend would, in fact, show up in the fall. What can happen is that institutions at the top of the "food chain" accept students from their wait lists, and these students in turn sacrifice their deposit to schools lower down the chain, generating vacancies and uncertainty. A downside to wait lists is that by the time a student is accepted, there may be much less money available for scholarships or grants. There was a report in The Wall Street Journal of a few colleges, such as Franklin & Marshall, that deliberately waitlisted overqualified students on the assumption that, even if accepted, they would almost certainly not enroll. The alleged purpose was to boost the admissions yield rate--the percentage of students who accept a college's admissions offer--as a means to improve the college's overall performance on the influential US News college rankings.