The increase in total health care expenditures in France can be explained by three distinct factors : the purely demographic effect (namely, the increase in the proportion of elderly people, given that health expenditure is an increasing function of age) ; the changes in morbidity at a given age ; the changes in practices, for a given age and morbidity level (e.g technological progress). The aim of this paper is basically to disentangle, evaluate and interpret the respective effects of these three factors. [Extrait introduction p. 3]