How does multiperiod portfolio choice differ from single-period mean-variance optimization?

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AcadiFi · Accepted Answer

Single-period Markowitz optimizes mean-variance utility over one horizon, producing a static efficient frontier. Multiperiod portfolio choice considers the full lifetime investment problem with time-varying opportunities, labor income, consumption, and changing risk aversion.

Key extensions from single to multiperiod:

(1) Intertemporal hedging demand: Robert Merton showed in 1971 that investors with long horizons hold additional positions to hedge against future changes in the investment opportunity set. If equity returns are mean-reverting, long-horizon investors hold more equity than the single-period optimizer because a bad decade is partially offset by a good decade.

(2) Human capital: a young analyst earning $110,000 with bond-like labor income has substantial implicit fixed-income exposure, justifying higher equity allocation in financial wealth. As retirement approaches and human capital depletes, financial portfolio shifts toward bonds.

(3) Consumption path: multiperiod models optimize consumption paths rather than terminal wealth. Epstein-Zin preferences separate risk aversion from intertemporal substitution, allowing investors to smooth consumption without distorting risk choices.

(4) Stochastic opportunity set: expected returns, volatilities, and correlations evolve. Campbell-Viceira's long-horizon framework uses VAR models to forecast returns and derives allocations that exploit predictability.

For Althea, age 42, earning $140k in stable employment with $425k in savings, a multiperiod allocation might be 72% equities versus 60% from a single-period view, reflecting her 20+ year horizon, bond-like human capital, and mean-reverting equity premium. CFA Level III candidates should connect this framework to goals-based investing, where each goal has its own horizon and allocation.

How does multiperiod portfolio choice differ from single-period mean-variance optimization?

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