The evolution of Yale University’s endowment fund has become something of legend, as described in a recent article in Chief Investment Officer.

In the mid-80’s, as the story goes, the Ivy League university’s CIO David Swensen shifted the $25.4 billion fund from a traditional mix of primarily bonds and a few equities into “carefully selected alternative investments—hedge funds, private equity, and venture capital—using external managers to capture the so-called illiquidity premium.” It was a good move for Yale, adding $7 billion of value and earning a 12.9% annual return over the past 30 years. The success has made what has been coined the Yale Model part of the endowment world’s lexicon.

For the university, the asset allocation used under the model reflects close to 60% in illiquid investments, while the vast majority of colleges and universities have less than 20%. The article emphasizes, however, that it is not a one-size-fits-all approach. Some believe, in fact, that the model may be “broken.”

Like most investment strategies, the Yale Model is only one approach, and may not be suitable for every endowment fund situation. Margaret Chen, head of CA Capital Management, espouses patience when using any investment approach and says, “It is absolutely true that as of June 30, 2016, if you invested only in the S&P 500 index or 10-year treasuries over the past five years, you would have done better than the endowment model.” However, she argues, managers must look at longer term results.

Scott Pittman, CIO of the Mount Sinai Medical Center, explains, “The [Yale] endowment model gets misrepresented as a static blueprint for portfolio management,” he says, adding, “it’s more of an innovative approach to how institutional investors should approach markets and think about opportunities and risks.”