The problem of measuring benefits arises in the health sector with a vengeance because there is an overwhelming and nearly universal reluctance to attach monetary values to health benefits and especially to value life in monetary terms. As a result, the outcomes of health projects are not usually measured in monetary terms, but in some other unit and the measure of effectiveness relate non-monetary benefits to costs. That is, we do not usually calculate the NPV of a project, but rather assess the cost-effectiveness of the intervention.
The simplest measure of outcomes in health projects is in terms of the outcome that the project seeks, as in the number of vaccines delivered. The main shortcoming of such measures is that they focus the attention on the intervention itself and not on the results of the intervention. Vaccines are delivered in order to prevent illness and premature death, and they are effective only in so far as they achieve their ultimate aim. A more appropriate measure of the benefits of a project that delivers vaccines is its effectiveness in preventing illness and premature death. Years of potential life gained (YLGs) is a measure of benefits that more accurately measures the effects of interventions and are calculated as the difference between the expected duration of life with and without the intervention. YLGs, however, do not take into account the benefits obtained from the prevention of illness.
Healthy years of life gained (HYLGs) take into account the gains stemming from preventing illness as well as premature death and they are defined as the sum of years of life gained on account of reduced morbidity and mortality, with morbidity adjusted for disability. Other measures of benefits
HYLGs count a year of life gained by a young person the same as a year of life gained by an old person. DALYs (disability adjusted life years gained), on the other hand, weight HYLGs by age. The weights vary by age group, are highly subjective, and may vary across cultures and social contexts. Consequently, DALYs are controversial. QALYs (quality adjusted life years) count a fully functional year of life as one