Life is priceless to those who possess it. Policymakers, though, must take a more hard-headed approach. That is particularly—if unfairly—true in poorer parts of the world.【T1】It is important for the authorities to understand the cost-effectiveness of a health program, so that its value can be compared with that of other claims on the public purse.

How to go about doing this is illustrated by a paper published in The Public Library of Science by Kartik Venkatesh of Brown University and Jessica Becker of Yale.【T2】Dr. Venkatesh and Dr. Becker asked themselves if it would be a good idea for the government of India to try, at regular intervals, to test the country’s population for HIV, the virus that causes AIDS, in order to treat those who unknowingly harbor it. The short answer is that, if it were feasible, it would be.

【T3】 Though HIV in India has not turned into the widespread epidemic some experts feared it would a few years ago, it is reckoned to affect about 2.4m people, many of whom do not realize they are infected. If they were identified, these people could be given antiretroviral drugs to stop the symptoms of AIDS developing. That would also have the bonus of reducing the chance of their passing the virus on.

The calculations made by Dr. Venkatesh and Dr. Becker rely on a model developed by the World Health Organization and already in use in America, France, South Africa and elsewhere. It values lives extended and saved, and further infections and other treatment avoided. It then balances those against the costs of testing people and of giving drugs to those who test positive (plus the inevitable extra non-HIV spending that typically follows testing).

【T4】The price at which an extra year of life saved is deemed cost-effective is anything less than triple the annual GDP per person of the country in question. In India that is $3900. Anything below parity ($1300 per year of life) counts as very cost-effective. According to Dr. Venkatesh and Dr. Becker, testing Indian adults every five years would cost $ 1900 per year of life saved, and would thus pay off handsomely.

Whether it could actually be done is another matter.【T5】But India takes AIDS seriously and the fact that the epidemic has not run out of control in the way that was once feared is at least in part the consequence of the country’s policies. The will to test therefore probably exists. Dr. Venkatesh and Dr. Becker suggest it would be worth finding the means, as well.

【T1】