Adding The Time Dimension: Optimal Rebalancing

Abstract

A technique called dynamic programming can be used to identify an optimal rebalancing schedule, which significantly reduces rebalancing and sub-optimality costs. Dynamic programming provides solutions to multi-stage decision processes in which the decisions made in prior periods affect the choices available in later periods. Dynamic programming provides the optimal year-by-year decision policy by working backwards from year 10. The results of the test of the relative efficacy of dynamic programming and the MvD heuristic with data on domestic equities, domestic fixed income, non-US equities, non-US fixed income, and emerging market equities, show that the MvD heuristic performs quite well compared to the dynamic programming solution for the two-asset case and substantially better than other heuristics. The increase in the number of assets reduces the advantage of dynamic programming over the MvD heuristic and is reversed at the level of five assets. Dynamic programming cannot be applied beyond five assets, but the MvD heuristic can be extended up to 100 assets. The MvD heuristic reduces total costs relative to all of the other heuristics by substantial amounts. The performance of the MvD heuristic improves relative to the dynamic programming solution as more assets are added but this improvement reflects a growing reliance on an approximation for the dynamic programming approach.