The GiveWell Blog

Bringing the Economic Benefits of Reading Glasses into Focus

It started in my early forties, and it’s only gotten worse since then. At first, it was a mild annoyance, but now it affects my quality of life and makes it harder to get things done. I’m definitely not alone—almost every middle-aged person I know has the same problem—and maybe you do too: a condition called presbyopia, a type of age-related vision loss that makes it difficult to see things clearly at close distances.

Luckily, the condition is easily and inexpensively treated with reading glasses, widely available at nearly every corner drug store in the United States. Reading glasses work well, and they’re cheap enough that I have them stashed around my house so a pair is always in reach. But an estimated 510 to 826 million people around the world have presbyopia but do not have corrective glasses.

What we know and what we don’t know

We think that providing reading glasses to people who need them is a promising way to improve their employment opportunities and increase their economic well-being. It makes intuitive sense that being able to see better would improve people’s ability to work, particularly for vision-intensive jobs such as crop cultivation and inspection, manufacturing, or retail work.

Since we’re not as confident as we’d like to be in the effect of distributing reading glasses, we’re co-funding a study to find out more before we allocate significant funding to direct delivery of glasses. We’re recommending a $4.8 million grant for the study.

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Answering some questions about water quality programs

On June 22, we held a virtual event on research into water quality interventions, featuring presentations from Michael Kremer of the University of Chicago’s Development Innovation Lab; Brett Sedgewick from Evidence Action, the parent organization of Dispensers for Safe Water; and Stephan Guyenet, Elie Hassenfeld, and Catherine Hollander of GiveWell. (If you weren’t able to attend, we’ve published a video recording, audio recording, and transcript here.)

We hosted the event to provide some additional background for our recommendation of up to $64.7 million to Dispensers for Safe Water, which installs chlorine dispensers to treat water at rural collection sites in Kenya, Malawi, and Uganda. This grant was the result of a lengthy investigation and a significant update in our views on the cost-effectiveness of water treatment, which we’ve written about here.

Several attendees wrote in with a range of thoughtful questions—about our analysis of the effects of chlorination interventions, about the particulars of Dispensers for Safe Water’s program, or more generally about our work. We covered as many as we could during the event and followed up on others by email. Below, we’re sharing a selection of the questions we responded to in writing, along with other questions we’ve gotten about this work outside of the event, in the hope that they’ll be of interest to a broader audience. Questions and answers have been anonymized; some have been edited slightly for brevity, or to fill in important context that was missing.

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How we evaluate a study

We previously wrote about our general principles for assessing evidence, where “evidence” is construed broadly (it may include awards/recognition/reputation, testimony, and broad trends in data as well as formal studies). Here we discuss our approach to a particular kind of evidence, what we call “micro data”: formal studies of the impact of a program on…

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Development experiments (randomized controlled trials) as a counterpoint to marketing materials

There’s been a minor flurry of recent blog posts about randomized controlled trials (RCTs) in international aid, including William Easterly’s take and responses by Chris Blattman and GiveWell Board member Tim Ogden. A central theme has been the difficulty of generalizing from one experiment to whether something “works in general.” There seems to be a…

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