The 2017 Yale University annual report argues in favor of active management strategies used by the investment offices of the country’s ivy league schools, according to a recent article in Institutional Investor.

In the report, Yale rebuts Warren Buffett’s suggestion–stated in his 2016 letter to Berkshire Hathaway shareholders, that endowments and other institutional investors would be better off investing in an index like the S&P 500—by claiming that the top ten U.S. university endowments “amaze,” and that “their well-diversified portfolios crush the returns produced by U.S. stocks.”

For the 20-year period ending June 30, the article reports, “Yale’s endowment earned a 12.1 percent annualized return, beating its benchmark Wilshire 5000 stock index, which gained 7.5 percent. A passive portfolio with a 60 percent stock allocation and 40 percent in bonds, meanwhile, had a 20-year return of 6.9 percent.”

“The superior results of Yale and a number of peers strongly suggest that active management can be a powerful tool for institutions that commit the resources to achieve superior, risk-adjusted investment results,” the report states. With specific reference to Buffett’s argument, it adds, “In advocating the adoption of a passive indexing strategy, Buffett provides sound advice for the vast majority of individuals and institutions that are unable (or unwilling) to commit the resources (human and financial) necessary for active management success.” But the argument doesn’t apply to endowments such as Yale’s that “possess the capabilities to pursue successful active management programs.”