The endowment model is an investment approach, pioneered at university endowments such as Yale’s, that commits a large share of a perpetual portfolio to illiquid alternative assets — private equity, venture capital, hedge funds, and real assets — funded by a time horizon few other investors can match.
In plain terms
An ordinary portfolio holds mostly public stocks and bonds that can be sold on any given day. The endowment model trades a chunk of that liquidity for stakes in markets where capital is locked up for years, on the theory that illiquidity itself is compensated with a higher return, and that an institution which never has to retire and spends only a small fraction of its assets each year can afford to wait it out.
How it works
The approach is associated with Yale’s investment office, which began shifting the university’s endowment heavily into private equity, venture capital, and absolute-return strategies starting in the mid-1980s; other university and foundation endowments copied the template in varying degrees over the following decades. Mechanically, the portfolio commits capital to closed-end private funds years before that capital is actually invested — a capital call draws it down over time — and accepts a multi-year J-curve of flat or negative reported returns while the capital is deployed and the fund’s early fees are paid. Success is measured over a full market cycle rather than a calendar year.
Spending is smoothed by formula, typically a percentage applied to a trailing multi-year average of the portfolio’s value, so a single bad year doesn’t force an immediate budget cut and a single good one doesn’t trigger a spending spree. Access to the underlying private funds usually requires the endowment — or a family office built to resemble one — to qualify as a qualified purchaser under the $25 million institutional threshold, since most large private funds in the United States are organized to accept only qualified purchasers.
The numbers
Per the 2025 NACUBO-Commonfund Study of Endowments, covering the fiscal year ended June 30, 2025:
- 657 institutions reported a combined $944.3 billion in endowment assets.
- Average allocation to alternative investments: 54.5% of the portfolio — 16.8% private equity, 15.4% marketable alternatives (hedge funds), 12.2% venture capital.
- Average allocation to public equities: 31.5%. To fixed income: 11%.
- Average one-year return: 10.9%.
- Average effective spending rate: 4.9%, up from 4.8% the prior year.
- The allocation scales sharply with size — per NACUBO’s size-cohort tables, endowments under $50 million held about 12.5% in alternatives in 2025, versus roughly 62.5% for endowments over $5 billion.
What people get wrong
That the “endowment model” is a strategy a smaller investor or family office can copy by simply buying more private equity and venture funds. The NACUBO data makes the real driver obvious: allocation to alternatives doesn’t track sophistication, it tracks size and time horizon. An endowment under $50 million holds roughly a fifth of the alternatives allocation of one over $5 billion — not because its managers are less capable, but because a smaller, less permanent pool of capital can’t absorb a decade-long lockup or one bad vintage year without disrupting the spending it exists to fund. Access is also gated directly rather than just by appetite for risk: most of the funds that make up the “model” are built to accept only qualified purchasers, so the model is structurally unavailable below a certain size regardless of how patient an investor claims to be.
Related
Read more: Family Office: How the Very Rich Organize Their Lives and Money · Alternative Assets: Investing Beyond Stocks and Bonds
See also: Qualified purchaser · Capital call · J-curve