According to data released this week, both Harvard and Princeton universities saw record numbers of applicants for the class of 2011, a stark departure from the 9.7 percent decrease in applications to Yale.

The number of applications increased by 8 percent from last year at Princeton, while Harvard’s applicant pool increased 0.7 percent. Two weeks ago, Yale Dean of Admissions Jeff Brenzel announced that the number of applications to Yale decreased from last year’s record-high of 21,101 to 19,060. Counselors and admissions consultants offered various theories as to why Yale saw a decline while Harvard and Princeton did not, but most agreed that these shifts are due to normal fluctuations in the admissions process.

Harvard received 22,796 applications for the class of 2009, dropped slightly to 22,753 for the class of 2010, and this year, received a record-high 22,920 for the class of 2011. Princeton received 16,516 applications for the class of 2009, 17,478 for the class of 2010, and 18,891 for the class of 2011.

Brenzel said he does not believe it is useful to examine yearly changes in the number of students applying to top schools.

“I think it is a mistake to look for a cause in year to year changes in application numbers,” he said. “There are simply too many variables and too much random variation.”

Last fall, when early applications to Yale decreased by 13 percent, Brenzel suggested several reasons for the decline, including a response to last year’s Ivy League record-low acceptance rate and the publicity Harvard and Princeton received in September for their decisions to eliminate early admissions next year. Yale announced in January that it would retain its single-choice early action option for the next year. In addition, the University decided not to include hard copies of applications in packets mailed to prospective students this year, which may have been a factor in the number of students who chose to apply.

Last year, Yale accepted 8.6 percent of applicants, while Harvard accepted 9.3 percent and Princeton accepted 10.2 percent.

Some counselors echoed Brenzel’s theories, saying Princeton may be increasingly seen as an appealing and realistic option for students worried about their chances of getting into Yale.

Beth Slattery, a college counselor at the Harvard-Westlake School in Los Angeles, Calif., said there is a tendency for applicants to stop applying when they simply believe they do not have a chance of acceptance.

“A perception that people might have may be due to Yale having the lowest acceptance rate in the Ivies,” she said. “Perhaps kids have the perception that it’s the most challenging place to get into and that would deter them.”

Chuck Hughes, president of the college admissions counseling firm Road to College and a senior admissions officer at Harvard from 1995 to 2000, said Princeton may have become more popular with applicants because of recent efforts to increase ethnic and socioeconomic diversity among its student body. Although Yale and Harvard have also improved their financial aid policies in recent years, he said, Princeton’s image has always lagged among the Big Three due to perceptions that the school is overly homogeneous, and these recent efforts likely helped to counter this perception.

Last year, Harvard announced it would eliminate the parental contribution for students from families with annual incomes below $60,000 and reduce the parental contribution for students from families earning between $60,000 and $80,000 a year. In March 2006, Yale eliminated the parental contribution for students from families earning under $45,000 and reduced it for families earning between $45,000 and $60,000 per year. Last year, 55 percent of Princeton’s incoming class received some form of the university’s need-based, no-loan financial aid.

Hughes said the media attention surrounding Harvard and Princeton’s decisions to eliminate their early admissions programs likely generated positive publicity for the two schools. In addition, students following acceptance trends were probably irrationally discouraged from applying to Yale.

“Kids are making macro-assessments and saying, ‘I have a 1 percent better chance at Harvard and Princeton so I’ll apply there,’” Hughes said.

High school students said Princeton was seen to be more attractive this year in part because of Harvard and Yale’s selectivity. Stephanie Martin, a senior at Phillips Academy Andover in Massachusetts, said her classmates at Andover have increasingly seen Princeton as a more realistic goal.

“I feel like some people were more intimidated by Harvard and Yale this year, and I think the perception is that fewer people apply there in general, so they thought less competition from other Andover students would be a good way to sneak into a top Ivy,” she said.

But counselors said even 10 percent shifts in application numbers mean little unless they are part of a larger, long-term trend.

David Hawkins, director of public policy for the National Association for College Admission Counseling, said it is not unusual for application numbers to fluctuate. For example, Harvard’s applications actually decreased for the class of 2010 from the year before.

“At the level that we’re dealing with in terms of caliber of students, attentiveness to the admissions process and their knowledge of it, as well as advice from their helpers, may have had some role in [these changes],” he said. “But I think the bulk of it can be attributed to the volatility of the admissions process.”

Patterns over the next few years would be worth examining, said Amy Sack, president of the college admissions consulting firm Admissions Accomplished.

“Unless the trend continues next year for Yale and doesn’t for the other schools, then I might think something else is going on,” she said. “But after a record-breaking year, it wouldn’t be unusual for applications to Yale to go down.”

All the other Ivies for which statistics are available saw increases in their applicant pools.

Columbia University received 21,303 applications for their Class of 2011, a 7.3 percent increase over last year. Brown University reported a rise of 3.8 percent, for a total of 18,951 applicactions. Cornell’s pool increased by 7.5 percent to 30,191, and University of Pennsylvania Dean of Admissions Lee Stetson said Penn received approximately 22,500 applications, marking a 10 percent increase. Dartmouth College does not release its numbers until it announces how many students it accepted.