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We have found that there is a great deal of quantitative evidence on the cost-effectiveness of different health interventions. Much of our data comes from two excellent reports which are produced by the world's leading bodies on the cost-effectiveness of global health. The DCP2 is produced by the Disease Control Priorities Project and WHO-CHOICE is produced by the World Health Organisation.
In order to work out the most effective health interventions, we need some way to compare the benefits that different interventions would have. One measure is the number of lives saved, but it is a truism that you can never really save someone's life, since they will still die at some later time. All you can do is to extend their life for a while. A better measure would thus be the total number of life-years saved. On the other hand, some interventions don't even save life-years, but instead improve the quality of people's lives by preventing or curing illness. An ideal measure of the effectiveness of health interventions would thus take into account improvements to both quantity and quality of life.
Disability Adjusted Life Years (DALYs) offer a way to do this. They are a measure of lost health due to illness used by the World Health Organisation. One DALY represents the equivalent to losing a year of life at full health. Each illness has a disability weight assigned to it, representing the amount it reduces a person's quality of life. For example, a year of life spent with blindness counts for 0.6 DALYs. Preventing 10 years of blindness is thus worth the same amount as letting someone live for six more years at full health. DALYs aren't a perfect measure of health outcomes, but they are very versatile and serve as a useful rough guide. For further information see the WHO's definition.
Although we find the cost-effectiveness estimates provided by DCP2 and WHO-CHOICE to be important and helpful, they should be taken with a grain of salt. GiveWell found serious calculation errors in the DCP2’s estimate of the cost per DALY averted for deworming, and we don’t know how widespread such errors are. The deworming estimates were among the first of their kind, and so were particularly prone to error, in contrast with figures for HIV, TB and malaria, which have been conducted many times. More generally, these estimates are subject to regression to the mean, and the most impressive estimates are likely to be less cost-effective than their estimates suggest. One reason to expect them to overstate the good done by additional donations today is that the most important treatments are often already being delivered. Vaccinations, for instance, are amazingly cost effective, but are already delivered in most cases where they easily can be. Further funding for vaccination today tends to go to hard-to-reach areas or less essential vaccines, where you would expect the cost effectiveness to be somewhat lower.
Since it is so versatile, the DALY is the primary unit of both the DCP2 and WHO-CHOICE reports. We can thus present a survey of these results in terms of the following chart, where the bars represent the cost-effectiveness of each intervention type, measured in the number of DALYs averted per $1,000 spent, so longer bars are better.
To find out much more about the interventions, see our individual pages on:
- Neglected tropical diseases (NTDs)
- Maternal Mortality
- Health Education
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