# The GiveWell Blog

Every month we send an email newsletter to our supporters sharing recent updates from our work. We publish selected portions of the newsletter on our blog to make this news more accessible to people who visit our website. For key updates from the latest installment, please see below!

If you’d like to receive the complete newsletter in your inbox each month, you can subscribe here.

# Raffles, Deworming, and Statistics

Sometimes statistics can help when it’s hard to decide what to do.

You’re at a local art fair, and they’re raffling off a car worth $10,000. Five hundred tickets are being sold, each for$10. Does it make financial sense to buy a ticket? (For the moment, let’s set aside other questions about raffles and just focus on the benefit for you, the potential ticket-buyer.)

You can use a statistical concept called “expected value” to help you decide. Expected value is calculated by multiplying the probability of each potential outcome by its value, then adding these results together to get the average result of an action.

Let’s figure this out—a car is on the line. First, we multiply the probability of each potential outcome by its value.

# 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.