NEW YORK (CNNMoney.com) - The most richly endowed colleges and universities in North America got even richer last year, according to the latest data available from the National Association of College and University Business Officers.

The average endowment fund grew by 9.3 percent during the year through June 30, but most of the wealthiest schools achieved a far better return. The 56 colleges with more than a billion in endowment funds (see table below) earned about a 13.8 percent return, while colleges with endowments of less than $25 million earned under 9 percent.

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Harvard, the wealthiest North American university, saw its endowment climb 15 percent to more than $25 billion. Second place Yale did even better on a percentage basis, growing its fund more than 19 percent, to $15 billion. Stanford's endowment grew 23 percent.

Nine institutions joined the billionaire's club over the 12 months through June 30, with the University of Toronto vaulting 24.4 percent to more than $1.2 billion. Other newcomers included Amherst, University of Wisconsin, and Baylor.

No schools dropped out of billionaire status but one, Emory University, lost money during the 12 months. Its endowment dropped 3.5 percent to under $4.4 billion, still good enough for 11th place on the list. Emory's endowment rises and falls with the fortunes of Coca-Cola; a significant share of their fund is in Coke stock.

What are the proceeds from endowment funds being spent on? The salaries of their professors, for one. Click here to see how much the average professor earns. Also see the most expensive colleges.