While the number of early applicants to Yale this fall dropped by 13 percent from last year, Harvard and Princeton Universities saw slight increases in the size of their early application pools.

Yale administrators, college admissions experts, and high school college counselors said they are unsure why Yale experienced the dramatic drop, and few were able to pinpoint specific factors with confidence. High school seniors cited a variety of individual factors — such as Yale’s downscaled mailing campaign and specific academic or cultural differences between Yale and other schools — that influenced their decision-making processes.

In contrast with Yale’s decline, Harvard reported a 3.5 percent increase in early action applications, while Princeton received two percent more applications than last year to its early decision program. Other schools, including Stanford and Northwestern Universities, also saw slight increases in their early applications.

Yale College Dean of Admissions Jeff Brenzel attributed the 13 percent decrease to a number of factors, including Yale’s extremely low acceptance rate last year, the publicity Harvard and Princeton received recently after announcing the elimination of their early options starting next year, and Yale’s decision not to include hard copies of applications in its mailings this year.

Last year, 4,084 students applied early to Yale’s class of 2010 under the single-choice early action policy, and an Ivy League record-low 17.7 percent were accepted. The University received 3,541 applications for the Class of 2011 through its single-choice early action program this year, to which students applied by the Nov. 1 deadline.

Amy Sack, president of the college admissions consulting firm Admissions Accomplished, said she is unable to isolate any specific reasons for the decrease in Yale’s numbers. While an unusually low number of her clients are applying to Yale early or regular decision this year, she said fewer of her students are applying to Harvard and Princeton as well. Sack said she is surprised by Yale’s marked decline, though she considers the generally low acceptance rate of the most selective schools to be a deterrent for many students.

“Most of my students who would have applied to Harvard, Yale, and Princeton in the past have said ‘Forget it, I have a better shot at Cornell [University],’” she said. “But I’m not sure why [Yale’s numbers] changed so much, since nothing has drastically changed there.”

High school college counselors said they were also surprised by the nationwide drop in early applications to Yale, since they had not experienced a decline among students they advise.

Beth Slattery, a former University of Southern California admissions representative and current dean at Harvard-Westlake School, a private high school in Los Angeles, Calif., said she has not noticed any change in Yale’s reputation. Just as many seniors from Harvard-Westlake are applying to Yale as have in previous years, she said.

“Yale has in no way gone down in anyone’s estimation,” Slattery said.

Kevin Newman, associate director of college counseling at the private Brentwood School in Los Angeles, said Brentwood has not experienced a shift in applications to Ivies either. He said he does not think Yale’s record-low acceptance rate last year affected his students’ decisions. When Brentwood students are considering where to apply, he said, counselors try to focus on which school will be the best fit for the individual. With respect to national trends, Newman said, he believes application numbers are cyclical and that too much significance should not be placed on year-to-year statistics.

The public Berkeley High School in Berkeley, Calif. also had a similar number apply to Yale as last year, college advisor Ilene Abrams said. Students consider the merits of each specific college in their decision-making process, she said.

“I don’t think [Berkeley High students] see the difference between Harvard and Yale in terms of acceptance rates when deciding where to apply,” Abrams said.

Students who chose not to apply to Yale said there were a number of individual reasons behind their decisions, but failed to identify any broader causes.

Alex Andrews, a senior at the Hopkins School in New Haven, said she did not think about Yale’s low acceptance rate when applying to college. Instead, she said, she considered Yale and Harvard both to be attractive and ultimately made the decision to apply early to Harvard based on differences between the universities’ athletics programs.

Scout Sanders, a senior at Hopkins who did not apply to any colleges early, said there might be merit to arguments that the decrease in Yale’s numbers was due to the omission of the hard-copy application in mailings.

“I don’t think it really affects much, but I noticed that Yale was pretty stingy with mailings compared to other schools,” she said. “Other schools would send something in the mail every day, like big glossy viewbooks, but Yale didn’t send much.”

Sanders disagreed with the view that the change in Yale’s numbers resulted from the publicity and media attention given to Harvard and Princeton’s eliminations of their early admissions programs.

“I think all three of the schools — Yale, Harvard, and Princeton — are such big names and such good places that I don’t think one publicity instance would really change things,” she said.

Students who did apply early to Yale said they did so because of a strong desire to attend, and that their decisions were unaffected by fears of intense selectivity. Both Alexandra Espinoza, a senior at Fort Worth Country Day School in Texas, and Daniel Lao, who attends Notre Dame Catholic High School in Fairfield, Conn., said they were unaware of Yale’s low acceptance rate last year.

“When I was researching Yale, I really liked the facilities and how everything is focused on undergrads,” Lao said. “By applying early I can find out my admission and financial aid status and know before the new year how much money I can get and how much I need.”

Brenzel said he does not place much significance on year-to-year variances in numbers due to the great increase in applications to all of the Ivy League schools over the past 10 years.

“The landscape will change significantly next fall whether or not we retain our own early admissions program, so this fall’s outcomes are unlikely to yield useful information about what will happen next year,” he said.

Yale is expected to come out with a decision concerning its early admissions program in January.

Brown University experienced a 2.6 percent decrease in its number of early decision applications this fall. Columbia University, Cornell University, Dartmouth College and the University of Pennsylvania have not yet released their early admissions figures.