With college acceptance rates continuing to fall this year, college counselors and admissions experts say they expect the race to get into college will only become more unpredictable.

Among the Ivy League schools, Yale was the only school whose admissions rate remained unchanged from last year, admitting 1,940 of 25,869 applicants and waitlisting 932. All other Ivies saw a decline in their acceptance rate, with Harvard posting a record low 6.9 percent. For the first time in recent memory, Stanford replaced Yale as the second most selective college in the nation with an admit rate of 7.2 percent. In addition, while Yale’s acceptance rate remained steady, the University admitted fewer students this year in proportion to the slight decrease in applications, out of concern that too many students would matriculate, said Jeff Brenzel, Dean of Undergraduate Admissions.

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While seven of the eight college counselors and admissions experts interviewed said they were not surprised by this year’s record low acceptance rates, five said they are now having difficulty predicting where students will be accepted to college.

“Last year, we ended up taking only seven students from the waiting list. To keep from having too many students enroll, we wanted to be a little more conservative this year,” he said. “The size [of the waitlist] fluctuates primarily with our judgment about individual students.”

Each year, Yale waitlists the number of students it thinks it may want to reconsider later, he said.

David Hawkins, public policy director of National Association for College Admission Counseling, cautioned against placing too much emphasis on a college’s selectivity, noting that the fractional falls seen this year can be attributed to factors as minor as, for example, a small change in an application question.

Still, Hawkins noted that colleges face pressure to keep acceptance rates low. Colleges may be keeping a large waiting list pool to fill up their incoming class if too few students matriculate, he added.

“A large part of a college’s reputation both from an admissions perspective as well as among students and alumni comes from its selectivity,” Hawkins said. “If a college drops a few points in selectivity, it may fall in external rankings — something that admissions offices do not like very much.”

Skip Zickmund, college counselor at Mullen High School in Denver, Colo. echoed Hawkins’s concern, suggesting that top-tier schools such as Stanford, Harvard and Yale are “walking lockstep with each other” by admitting fewer students than they otherwise would.

Kate Augus, director of college counseling at the Head Royce School in Oakland, Calif., said a college’s selectivity has a substantial impact on its perceived prestige and is an important factor for many parents and students during the application process, contrary to the advice she gives them.

“The lower acceptance rates this year means that more students are finding themselves on waiting lists and that creates stress for the student throughout summer leading up to enrollment,” Augus said. The anxiety is increased by the fact that students must make a firm commitment to a college by May 1 even if the college they have been accepted to is not one of their top choices, she added.

Still, waiting lists are playing an important role in college admissions by allowing colleges to maintain the quality of their incoming class in a time when it is increasingly difficult to predict which students will matriculate, Hawkins said.

“Keeping a large waiting list pool means that a college can meet the incoming class quota but also admit the right students,” he explained. “For instance, a school may wish to admit students from a certain region or students with a particular interest or talent.”

Around two-thirds of students waitlisted by Yale choose to stay on the waiting list, Brenzel said. Of those who are eventually offered a place, waitlisted applicants matriculate at a slightly higher rate, he added.

Students accepted to Yale’s class of 2014 have until May 1 to make a decision whether to matriculate this fall.

Correction: April 10, 2010

An earlier version of the graph accompanying this article misrepresented the admissions rates for the Yale classes of 2010 and 2011. The current graph represents the correct rates.