After Harvard’s applicant pool soared to a record high in December, the College’s acceptance rate plummeted to a record low yesterday.

7.1 percent of applicants were accepted to the Class of 2012, according to figures the Admissions Office released yesterday. Just under 9 percent were admitted last year.

This year, 1,948 high school seniors will receive big envelopes from the admissions office—110 fewer than last year.

The admitted students were selected from a pool of 27,462 applicants, reflecting an 18-percent increase from 22,955 last year.

A record 11 percent of the admitted students come from African American backgrounds. Over 18.5 percent are Asian American, 9.7 percent are Latino, and 1.3 percent are Native American. Just over half of the admitted students are women.

Recent financial aid initiatives at Harvard and other colleges, as well as Harvard’s elimination of early action, made it particularly difficult for the admissions office to predict how many students would enroll this year, according to Dean of Admissions and Financial Aid William R. Fitzsimmons ’67.

As a result, Harvard accepted fewer students to avoid over-enrolling its freshman class, Fitzsimmons said.

Space has been another major concern, with a two-year moratorium on transfer students announced last month.

Fitzsimmons said that the admissions office might be relying more than usual on the waitlist—which numbers in the “many hundreds”—to fill up the Class of 2012.

“Honestly, nobody knows what’s going to happen,” he said. “No matter how many mathematical models one might use, there’s just too much uncertainty.”

With the larger pool of applicants this year, Fitzsimmons said decisions were particularly difficult in some cases.

“I think we had more people at the margin about whom we really agonized,” he said. “I just thought we had good choices across the board, which, of course, made it painful to make the decisions.”

One student accepted to the Class of 2012, Ben M. Schenkel of Bethlehem, Pa., said he kept hitting the refresh button while waiting for his e-mail from the admissions office yesterday afternoon.

When his acceptance e-mail finally popped up on his computer screen, Schenkel said he reacted with “a combination of hooting and fist-pumping and kicking my legs up in the air.”

The percentage of students interested in engineering also rose again, from 9.5 percent last year to 11 percent this year—an increase Fitzsimmons attributed to the attraction of Harvard’s new School of Engineering and Applied Sciences.

In December, Harvard announced sweeping changes to its financial aid program, easing the cost of attendance for middle-income families. In a similar move, Yale announced soon afterward that the university would increase financial aid for middle-income families. In response, other schools, such as Brown and Stanford, have also launched plans to boost financial aid packages for undergraduates.

The socioeconomic makeup of the Class of 2012 is not yet clear, partially as a result of the elimination of early action, which made many families less anxious to get in their financial aid forms early, according to Fitzsimmons.

This is Harvard’s first year without an early action program, which Fitzsimmons said benefited students from wealthier school districts where they received better preparation for the admissions process.

As of now, over 25 percent of the Class of 2012 is eligible for Harvard’s old financial aid program, which eliminates tuition costs for families earning under $60,000.

The average financial aid package this year is about $40,000, close to 78 percent of the total cost of attendance.

Admitted students will be able to get a taste of the campus and student life during the April visiting program from April 25 to 27. Typically, about 1,200 students visit during the month of April, with around 1,100 attending admitted students weekend.

The accepted students will be contacted by members of the Undergraduate Admissions Council, congratulating them and answering questions, as well as the Undergraduate Minority Recruitment Program, Harvard Financial Aid Initiative, teaching faculty, and admissions and financial aid staff.

Admitted students must reply by May 1 to accept or decline their spot in the Class of 2012.

—Staff writer Lingbo Li can be reached at lingboli@fas.harvard.edu.