Yale disclosed Tuesday that its endowment had fallen at least 13.4 percent in the four months since June as the decline in asset values during the financial crisis takes its toll on another university.

Richard C. Levin, Yale’s president, said in a letter to the university’s faculty and staff that the endowment totaled about $17 billion, and he warned that Yale could be facing a $100 million shortfall in the 2009 school year.

He said the value of Yale’s marketable securities had declined 13.4 percent for the first four months of the university’s fiscal year, which started July 1, and that it had since fallen even more. Taking into account such illiquid assets as real estate and private equity, he said, the endowment, which is led by David Swensen, was down 25 percent, and Yale is now anticipating it will be down that much for its full fiscal year.

That figure is significantly better than Harvard’s endowment, which recently said that the value of its $36.9 billion endowment had fallen 22 percent during the same period and that the total decline for the full fiscal year is expected to be as much as 30 percent.