# 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.

# What If We Have Extra?

What do you do if you’re in the very fortunate position of having more money than you need to meet your own immediate needs? You might find new things to buy. You might stockpile it for a rainy day. You might donate it to cost-effective global health programs. Or you might do some combination of the three.

GiveWell thinks about that same question.

First, a bit of context: All donations made to GiveWell’s Top Charities Fund, All Grants Fund, and recommended organizations go to the programs we recommend. (We do not take a percentage of donations made to recommended organizations through GiveWell’s website, nor do we receive any fees from organizations for being featured on our site.)

Our own organizational needs are met by donors who choose to direct funding to GiveWell’s operations (by giving to our Unrestricted Fund). In other words, we are supported only by donors who explicitly choose to support GiveWell itself through unrestricted donations.

But what happens when we receive more unrestricted donations than we need? We could choose to spend the funds on something new for the organization. We could squirrel those funds away, building an endowment to cover future needs. Or, like you, we could donate to cost-effective global health programs.

# The fungibility question: How does GiveWell’s funding affect other funders?

How do GiveWell’s funding decisions influence the actions of governments, funders, and other organizations? Answering this question is an important part of figuring out which global health programs are most cost-effective and thus which we should support. We’ve already written about two key factors in our cost-effectiveness estimates: the cost per person reached and the overall burden. But those are only part of the equation.

We also consider what others are likely to do in response to our choices. For example, does our funding displace money the local government had planned to allocate to the program? Or would our funding make other funders more excited to join us in making sure the program is implemented?

Wedding registries provide a loose analogy about how one person’s decision might influence another’s: If someone already bought the toaster on the list, you’re probably not going to buy the lucky couple another one. The money that great-aunt Sally spent on the toaster has displaced the funding you had planned to allocate to the toaster: this is what we call “fungibility.”

In contrast, if the spouses-to-be have signed up for flatware service for 12 and only 6 settings have been purchased, you might prioritize filling out the remainder of the set, to be sure that the couple doesn’t run out of spoons at their upcoming dinner parties. In that case, the guests who purchased the first 6 settings can “crowd in” funding from other guests: this is what we call “leverage.”

# Increasing impact by combining programs

The idea has obvious intuitive appeal: If you’re already sending community healthcare workers door-to-door in (say) remote parts of Sierra Leone to deliver routine childhood vaccines, why not have those healthcare workers deliver chlorine for disinfecting drinking water, or oral rehydration solution for treating dehydration from diarrhea?

After all, if you’re already spending money on the fixed costs of delivery, why not provide other programs at the same time? You’d be able to amortize the costs across multiple goods and offer additional benefits to the community. (If you’re getting groceries delivered, it’s more efficient to have one driver deliver your eggs and milk and vegetables all together than to have separate drivers going round delivering each one separately.)

GiveWell is very interested in these “layered interventions,” and we are excited to support them wherever they cross our cost-effectiveness threshold. But we’ve discovered it’s harder than you might think to find ways to combine programs effectively.