Yale posted the toughest early admissions rate in the Ivy League in December, even as Harvard and Princeton reinstated early admission policies for the first time in four years.

The University admitted 15.7 percent of early action applicants for the class of 2016, which Dean of Undergraduate Admissions Jeffrey Brenzel said marked a slight increase from the previous year’s early acceptance rate of 14.5 percent. While the total number of 2011 early applicants to Yale declined about 18 percent from 2010, admissions experts said that results from the early application cycle are unlikely to impact the regular decision pool this spring or determine applicant patterns next fall.

“It is always hard to predict anything about the admissions pool,” Dean of Undergraduate Admissions Jeffrey Brenzel said in an email Wednesday. “I doubt that relatively small differences in admit rates or application numbers have much effect on who attends which of the top colleges.”

Yale admitted 675 of 4,304 early applicants and denied admission to 1,180 students. The University deferred another 2,394, or 55.6 percent of applicants, to the regular admissions pool in the spring — roughly the same percentage that was deferred in 2010. Yale will admit another 1,300 to 1,500 applicants in the spring from the regular pool and is aiming to have about 1,350 students enroll in the class of 2016, Brenzel said.

While Yale’s 2011 early applicant pool was smaller than last year’s, Brenzel said the University received more applicants this fall than the last time that Yale, Harvard and Princeton all offered early admissions programs in fall 2006. Harvard and Princeton accepted 18 percent and 21 percent of early applicants, respectively.

Jon Reider, a college guidance counselor at San Francisco University High School and former admissions officer at Stanford University, said the early admission rate differences between Yale, Harvard, Princeton and Stanford are “trivial” because they are widely regarded as their own elite grouping within the college admissions field.

Early admission statistics have far less influence on regular decision applications than the final acceptance rates posted by institutions in previous years, Reider said, adding that Yale, as a “highly desirable brand,” will always be competitive in the regular decision round.

In the rest of the Ivy League, Brown, Columbia, Cornell, Dartmouth and the University of Pennsylvania accepted 19 percent, 20.4 percent, 35.2 percent, 25.8 percent and 25.4 percent of their early decision applicants respectively. Stanford admitted 12.8 percent of its early action applicants.

Andrew McNeill, senior associate director of college counseling at the Taft School, a private school in Watertown, Conn., said results from the early admissions round do not forecast regular decisions. It will take several years to determine what effect Harvard’s and Princeton’s reinstatements of early admissions policies will have on future application cycles and yield rates, he added.

But Chuck Hughes, president and founder of Road to College, a college admissions consulting service, said the latest early admissions results could potentially increase applications to Princeton in fall 2012, since that school posted a higher rate of admission for early action candidates than peer schools Harvard, Yale and Stanford.

Yale will notify students who were deferred early acceptance and those who apply in the regular cycle of their admissions decisions on April 1.