The Divisia monetary index weights each monetary asset by itsexpenditure share, evaluated at its user cost.See Barnett et al. [1997, equations (5) and (6)].In a world of perfect certainty, the user costs can be computed directly from assetreturn data, and so, the index is model-free. In the presence ofuncertainty, however, the true user cost of a monetary asset dependson the covariance of the asset's return with the marginal utility ofwealth. Intuitively, an asset's value depends both on its expectedpayoff and on the asset's ability to hedge wealth fluctuations. As aresult, the true user cost cannot be computed without an explicitmodel of preferences. It follows that the exact Divisia monetaryindex in a stochastic economy is not model-free, but depends on theunderlying preference assumptions.