David Swensen

David Swensen was an American investor, born in River Falls, Wisconsin in 1954 into a family of academics. He studied at the University of Wisconsin-River Falls and completed a doctorate in economics at Yale in 1980, where his advisers included James Tobin and William Brainard.

He began his career on Wall Street. At Salomon Brothers he worked on the transaction generally described as the first currency swap, between IBM and the World Bank in 1981, and he later moved to Lehman Brothers. In 1985 Tobin and Brainard persuaded him to return to Yale as chief investment officer of its endowment, a move that involved a substantial cut in pay. He held the role for thirty-six years, until he passed away in 2021.

What he built there became known as the endowment model, or simply the Yale model. Its argument starts from the observation that an endowment has an effectively unlimited horizon and no requirement to meet redemptions, so it can hold assets that cannot be sold quickly and be paid for accepting that constraint. The portfolio moved heavily toward private equity, venture capital, real assets and absolute-return strategies, and away from domestic bonds and cash. The second half of the argument was that active management is worth paying for only in markets where information is poorly distributed, which is why the approach concentrated its active risk in private markets rather than in listed equities.

He wrote two books. Pioneering Portfolio Management, published in 2000, set out the institutional framework. Unconventional Success followed in 2005 and did something unusual: it told individual investors not to attempt any of it. His reasoning was that the model depends on access to a small number of exceptional managers that private investors cannot reach, and that without that access the approach imports the illiquidity and the fees while leaving the benefit behind. What he set out for individuals instead was a portfolio of low-cost index funds spread across a handful of asset classes and rebalanced on a schedule.

He also taught, at Yale College and the School of Management, and a notable number of the people who worked under him went on to run other university and foundation endowments.

Swensen treated portfolio construction as a question about the owner before it is a question about the assets. An endowment, a pension fund and a household have different horizons, different liabilities and radically different access to managers, so the same portfolio cannot be correct for all three. Most of his written work is an argument against copying a portfolio without first asking whether you share the circumstances that justified it.

For the institution, the reasoning ran through equity orientation and diversification. He argued that a fund with a long horizon should own assets with equity-like returns, because bonds and cash are a poor way to fund a perpetual spending commitment, and that the way to make a heavy equity orientation survivable is to spread it across sources of return that do not all move together. Illiquidity was treated as something to be paid for rather than avoided, on the reasoning that a fund which never has to sell is being compensated for a constraint it does not actually face.

The active management question he answered by market rather than by preference. In listed equities, where information is widely distributed and costs are low, he thought the case for paying for selection was weak. In private markets, where the spread between good and poor managers is far wider, he thought it was strong. That is a claim about where skill can be found rather than about whether it exists.

For individuals he applied the same test and reached the opposite conclusion. Private investors cannot reach the managers the model depends on, pay retail fees, and buy funds sold by firms whose obligation runs to their own shareholders rather than to the investor. Given those facts, his conclusion was that the sensible portfolio is a small number of low-cost index funds across several asset classes, rebalanced on a schedule and otherwise left alone.

The endowment model was adopted very widely by universities, foundations and pension funds after Yale demonstrated it, to the point where it became the default framework for institutional investing rather than one option among several.

His argument to individuals had a separate life. Because it came from someone running a large active programme rather than from an index fund provider, Unconventional Success is frequently cited as the least self-interested version of the case for low-cost indexing.

A number of investment officers who trained under him went on to run endowments elsewhere, which spread the approach through people as well as through the books.