A man walks past an array of mosquito bed nets, put on display in Dupont Circle in 2009 by Nothing But Nets, a grass-roots campaign aimed at preventing malaria. (Marcus Yam/The Washington Post)

Catherine Hollander is the outreach associate at GiveWell.

GiveWell looks for the best deals in charity — the places that offer the biggest “bang for the buck” when it comes to lives saved or improved per dollar donated. Our work offers a way to approach the task of making a donation do the most good that it can. Quantifying amounts of good, however, is harder than it looks.

We’ve come across a lot of charities making claims in the eight years since GiveWell was founded. You’ve probably seen the advertising: “Your $5 donation can save a life!” Often, those statements don’t hold up under closer scrutiny. Some gloss over the facts (yes, $5 can buy a mosquito net to prevent malaria, but not every mosquito net saves a life), while others involve mathematical errors (in one instance, a widely cited cost-effectiveness estimate for deworming, a treatment for parasitic worm infections, was roughly 100 times off the mark). As a result, we’re cautious when assessing charities’ claimed cost-effectiveness and when making similar estimates ourselves.

Of the hundreds of charities and programs we’ve researched, we currently recommend four most strongly: Against Malaria Foundation, Deworm the World Initiative (led by Evidence Action), Schistosomiasis Control Initiative and GiveDirectly. Hours were spent vetting the academic research on their programs’ effectiveness, reviewing financial documents and seeking evidence of their impact on the ground, and these organizations are the best giving opportunities we’re aware of today when it comes to impact per dollar.

However, while we do our best to calculate what, exactly, a charity can do with the funding it receives, we also caution donors against putting too much stock in a single figure. Even our calculations rely on questions without perfect answers.

For instance: How strongly does the evidence that a program worked in one environment suggest that the same effect will be seen in another? A study published in 2004 found that recipients of deworming pills had higher school attendance than children who didn’t receive the pills, and later research linked deworming pills to higher income in the long term. But the rates of worm infections were much higher than usual during the study period, most likely due to El Niño weather patterns. In more typical years with fewer worm infections, the long-term effects of deworming might also not be as large. How much should we discount for that?

Another question to consider in cost-effectiveness estimates is how to weigh impact. A deworming program can improve lives, but malaria-preventing bed nets can save them. Evidence suggests that providing direct cash transfers to very poor individuals can increase their asset holdings and consumption (likely a good proxy, we believe, for improved quality of life), but that programs for adding iodine to salt can improve cognitive development in children. Making the choice between opportunities like these requires philosophical judgment calls for which there are no clear answers. We present a range of cost-effectiveness calculations on our Web site — as well as a detailed discussion of the inputs that went into them — to allow donors to come to their own conclusions based on their own intuitions on these questions.

Our cost-effectiveness calculations have grown more robust in the years since GiveWell’s founding, but because of their inherent uncertainty, they are only one input into our overall conclusions about an organization. Other factors, such as the organization’s transparency and ability to put additional donations to use, also affect our decision to recommend a charity.

We continue to improve our cost-effectiveness estimates because the process of developing them helps us compare the work of different charities and pushes us to ensure that we’ve thought through the relevant issues when we’re looking at a giving opportunity. We’re excited by the enthusiasm we see among effective altruists for evidence and measurement in the charitable sector, and despite the challenges of neatly quantifying “good accomplished,” we believe it’s possible to give with more confidence today than it was 10 years ago.

Read more about this topic:

Christine Emba: Effective Altruism: a primer

William MacAskill: Working for a hedge fund could be the most charitable thing you do.

William Schambra: Most Americans aren’t efficient philanthropists. That’s a good thing.

Gary P. Steuer: Could effective altruism destroy the arts?

Peter Singer: Excellence in opera or saving a life? Your choice.

Jeremy Beer: Traditional charity fosters love. Effective altruism doesn’t.