Proportional means regression for censored medical costs

The semiparametric proportional means model specifies that the mean functio n for the cumulative medical cost over time conditional on a set of covaria tes is equal to an arbitrary baseline mean function multiplied by an expone ntial regression function. We demonstrate how to estimate the vector-valued regression parameter using possibly censored lifetime costs. The. estimato r is consistent and asymptotically normal with an easily estimable covarian ce matrix. Simulation studies show that the proposed methodology is appropr iate for practical use. An application to AIDS is provided.