The Endowment Model and Modern Portfolio Theory

We develop a dynamic portfolio-choice model with illiquid alternative assets to analyze the “endowment model,” widely adopted by institutional investors such as pension funds, university endowments, and sovereign wealth funds. In the model, the alternative asset has a lock-up, but can be liquidated at any time by paying a proportional cost. We model how investors can engage in liquidity diversification by investing in multiple illiquid alternative assets with staggered lock-up expirations, and show that doing so increases alternatives allocations and investor welfare. We show how illiquidity from lock-ups interacts with illiquidity from secondary market transaction costs resulting in endogenous and time-varying rebalancing boundaries. We extend the model to allow crisis states and show that increased illiquidity during crises causes holdings to deviate significantly from target allocations.