Willingness to pay and cost of illness for changes in health capital depreciation.

The paper investigates the relationship between the willingness to pay and the cost of illness approach with respect to the evaluation of economic burden due to adverse health effects. The basic intertemporal framework is provided by Grossman's pure investment model, while effects on individual morbidity are taken to be generated by marginal changes in the rate of health capital depreciation. More specifically, both the simple example of purely temporary changes and the more general case of persistent variations in health capital depreciation are discussed. The analysis generates two principal findings. First, for a class of identical individuals cost as measured by the cost of illness approach is demonstrated to provide a lower bound on the true welfare cost to the individual, i.e. cost as given by the willingness to pay approach. Moreover, the cost of illness is increasing in the size of the welfare loss. Second, if one takes into account the possible heterogeneity of individuals, a clear relationship between the cost values supplied by the two approaches no longer exists. As an example, the impact of variations in either financial wealth or health capital endowment is discussed. Thus, diversity in individual type turns out to blur the link between cost of illness and the true economic cost.