Yale University’s endowment has dropped an estimated 25 percent — a loss of about $6-billion — since June 30, creating a shortfall of $100-million in next year’s budget, President Richard C. Levin announced in a letter to the university today.

The endowment stood at $22.9-billion on June 30. By October 31 it had fallen by 25 percent, and it has continued to decline since then, Mr. Levin said. Investment income from the endowment makes up 44 percent of Yale’s annual budget.

Yale’s endowment performance closely follows those at other wealthy universities, including Harvard, but is of particular interest because many university endowments have copied the “Yale model” of investing. That model, devised by David F. Swensen, the university’s chief investment officer, has helped Yale earn annual returns as high as 28 percent.

In his letter, Mr. Levin said that Yale would continue to provide financial aid and hire new faculty members, but that it would cut some nonfaculty jobs, preferably through attrition, and would reduce the size of salary increases, among other budget items.

Still, he said, the university remained in a strong position financially. “It is important to recognize that $17-billion is still a very large endowment,” he wrote. —Kathryn Masterson