Optimized charitable giving, evidence-based medicine, and the risk of thinking we can measure everything

The GiveWell logo, taken from their website.

I read an interesting blog post this morning on Wonkblog about how some people are getting jobs on Wall Street in order to save the world: the idea is to make as much money as quickly as possible, live on next to nothing, and then use the saved money to save the world more efficiently than one could by joining the Peace Corps or becoming a doctor.

The post discussed a website/organization called GiveWell that takes a very hard-nosed, analytical approach to how we should most efficiently use our charitable dollars to do good in the world. The ballet or the symphony is nice, but by buying bed nets to prevent malaria you could be saving children’s lives for very little money, so guess which GiveWell recommends you to donate to? They choose a small number of top charities among a large number they review, and they are very careful not to make claims that the non-top charities are not useful, only that there is very good evidence that the top charities are useful. I am truly impressed with the thoughtfulness of the approach and the quality of the research they seem to have done.

But – and there’s always a but – it struck me that there is a limit to this approach to charitable giving, and it is strikingly similar to a limitation of evidence-based medicine that I’ve been bumping into recently.

Obesity and mortality: challenging the conventional wisdom, part III: BMI is nearly useless

I’ve just written a couple posts critiquing the recent study in the Journal of the American Medical Association claiming that overweight people are at lower risk of mortality. This is the third and last, and will be a detailed exploration of why BMI is a bad metric of obesity.

I am certainly not the first to claim this, and indeed there are many researchers who have been defending measures such as waist circumfrence for years. But my point is not just to trash BMI, nor to defend another measure in particular (I think waist circumfrence is also a red herring), but rather to use BMI as an example of how shoddy thinking can lead to the adoption of poor metrics and thus serious public health consequences.