A new fellowship program in the sciences will allow the Graduate School of Arts and Sciences to admit more doctoral students this year.

Because the endowment plunged in the 2008 recession, the Graduate School has sought to reduce the size of its incoming classes in recent years, but a gift from the philanthropic Gruber Foundation will help support growth even as the endowment is still recovering. The school aims to have 531 first-year Ph.D. students this fall, an 11 percent increase over last year’s target class size, Director of Graduate Admissions Robert Colonna said in an email.

Still, the increase will not be distributed evenly across departments. Because the gift supports graduate students in the biomedical and biological sciences and in astronomy and astrophysics, those programs will see the largest growth, while admissions in the humanities and social sciences will remain relatively stable, said Richard Sleight, an associate dean of the Graduate School.

Applications to the Graduate School’s doctoral programs rose by 1.9 percent this year to 9,462, Colonna said. But because the University guarantees five years of financial support — a stipend plus tuition and fees — to all its Ph.D. students, the number of doctoral students Yale can admit is constrained by the value of the endowment. Science programs depend less on the endowment than humanities and social science programs because so much of their funding comes from federal training and research grants.

The new Gruber Science Fellowships will provide $2.5 million annually, which will allow the University to recruit more top students in the fields it supports, said Carl Hashimoto, an assistant dean of the Graduate School who coordinates the fellowships. The fellowships will cover recipients’ tuition and pay them a slightly higher stipend than what students typically receive. Forty-nine students received fellowships for this first time this fall, but in the future the Graduate School will probably offer the fellowships to between 20 and 25 students per year as a recruiting tool during the admissions process, Hashimoto said.

Meg Urry, chair of the Physics Department and director of the Yale Center for Astronomy and Astrophysics, said offering stellar students a “name” fellowship like the Gruber might make Yale’s offer of admission more attractive.

“It adds prestige, and it makes us more competitive [in the sciences] than we might otherwise have been,” she said.

Two directors of graduate programs in the biological sciences interviewed said they think the Gruber Fellowships will help them admit more international students. Federal training grants, which fund many science Ph.D. students in their first years of study, can only be used to support U.S. citizens, so Gruber funding will make it easier for Yale to support qualified students from abroad, said Charles Greer, director of the graduate program in neuroscience.

Recent changes in how federal training grants are administered will also allow Yale to boost its numbers of graduate students in the sciences, Sleight said. Training grants used to support students for their first three years of study, but now they will only support students for two years. If Yale continues to win the same amount of training grant money from the government, the money can be spread across a larger number of students, he said.

Beyond the effects of the Gruber Fellowships and the new rules for training grants, some programs will admit more students this year because they had low yields last year, administrators said. Because of what administrators called normal fluctuations in yields, only 443 doctoral students accepted offers last year even though the Graduate School’s target was 478, according to data from the admissions office.

The endowment earned a 21.9 percent return in the last fiscal year, but the income that will be available from the endowment this year and next year will be about the same as it was last year, Graduate School Dean Thomas Pollard said. In the absence of new funding sources such as the Gruber Science Fellowships, graduate programs cannot grow back to their previous levels unless the endowment continues to perform well. Yale decided to reduce its number of graduate students by about 10 percent after the endowment dropped three years ago, Deputy Provost for Academic Resources Lloyd Suttle said in an email.

“If the value of the endowment increases further, we can hope in the future for more funds to support additional graduate students,” Pollard said.

The last applications to Yale graduate programs were due Jan. 2. Applicants will be informed of admissions decisions in February and March.