The analysis of health insurance systems, and in particular those focusing on copayment schemes, rely on delicate empirical measures of elasticity of demand for health care.
This paper offers a critical survey of the empirical literature on the moral hazard assumption, according to which a more extensive health insurance coverage would lead to more expenditures.
After recalling that the large RAND Health Insurance Study, conducted in the US in the 70s, unambiguously concluded that the price elasticity for medical care was negative, especially ambulatory care, the paper stresses the limits of more recent studies undertaken on French data; these limits are inherent to the data or due to the econometric methods employed. Beside, evaluating the redistributive aspects of copayments and their impact on access to care would require more accurate measures of crossed price income elasticity.
Despite all those uncertainties, the lessons drawn from existing empirical studies make believe that the current French system of ticket modérateur (copayment scheme) is very far from being fair and efficient.