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Sources for Impact Calculator

Published: November 2020

In 2019, the most recent year for which we have complete data, the Maximum Impact Fund was the most commonly selected option for donations on GiveWell’s website.

How is this calculated?

Below, we'll refer to the different outcomes our top charities can achieve. Our top charities list divides into two broad categories:

Life-saving

  • Malaria Consortium's seasonal malaria chemoprevention program
  • Against Malaria Foundation
  • Helen Keller International's vitamin A supplementation program
  • New Incentives

Income-increasing

  • Evidence Action's Deworm the World Initiative
  • SCI Foundation
  • The END Fund's deworming program
  • Sightsavers' deworming program
  • GiveDirectly

Donation amount and frequency

  • One-time: If you enter a one-time donation, we'll use that donation amount to calculate the impact you can achieve.
  • Monthly: If you enter a monthly recurring donation, we'll calculate the total amount you would donate during one year of giving. We'll use your 12-month total to calculate the impact you can achieve.

Impact by output and outcome

In each case except GiveDirectly, we present two estimates: one based on the cost of each output and one based on the cost of each outcome. Outputs refer to the nearest-term, easiest-to-measure impacts the charities achieve, such as deworming treatments or insecticide-treated nets. Outcomes refer to the ultimate impact of the donation, such as saving a life or increasing someone's income, that results from the outputs.

We use cost per output and cost per outcome figures from our public cost-effectiveness model.1 This model does not yet include estimates for New Incentives; you can find those in our cost-effectiveness model for New Incentives. We divide your donation total (one-time or one-year, if recurring) by the cost of an output and an outcome to produce the results we show in the calculator.

Number of same-sized donations to save a life

For the life-saving charities we recommend, if the donation amount you enter is less than the total we estimate is needed to save a life, we'll show you the number of same-sized donations required to achieve that outcome.

For example, we use an estimate of $3,000 to $5,000 to save one life by donating to Malaria Consortium's seasonal malaria chemoprevention program (more on why we use a range below). If you enter a one-time donation of $1,000 into the calculator, you will see that between three and five same-sized donations are needed to achieve the outcome of one life saved.

For the income-increasing charities we recommend, we do not calculate a single, discrete outcome (i.e., one life saved). The cost per outcome is scalable, so there is no minimum.

Rounding

We round the impact numbers we share with you. We round because although we spend significant time on our cost-effectiveness analyses, we consider our estimates to be extremely rough, rather than highly precise. You can learn more about this here. We have a higher degree of confidence in our cost per output measures than our cost per outcome measures, as the former involve fewer judgment calls.

When rounding in our Impact Calculator, we choose the more conservative figure each time. For example, we round our estimate of the number of outputs provided down to the nearest whole number. If a donation is less than the amount we estimate is needed to achieve one output, the calculator will display "0" outputs achieved. We round the number of same-sized donations to save a life up to the nearest whole number on both sides of the range presented.

Ranges

We use a range when we share our estimates of the cost to save a life. This reflects the degree of precision we believe our model can estimate, as well as the range of cost-effectiveness that charities are likely to achieve across the countries they work in. Charities' cost-effectiveness can vary widely by geography, depending on the underlying burden of disease and the costs of operating in a given country.

For the income-increasing charities we recommend, we do not use a range for the outcome.

We do not use ranges for our estimates of the cost per output in either case.

Impact of malaria

Estimates of annual malaria deaths vary from about 400,000 to 620,000.2 At least 83% of the malaria deaths reported by the World Health Organization (WHO) for 2018 were in sub-Saharan Africa, and children under five years old accounted for about two-thirds of malaria deaths globally.3

Presuming the proportion of children dying from malaria is approximately constant across countries, then at least 56% of total malaria deaths were children under 5 years old in sub-Saharan Africa (83% of total malaria deaths in sub-Saharan Africa multiplied by 67% of total malaria deaths occurring in children under five).

Impact of vitamin A deficiency

The Institute for Health Metrics and Evaluation's Global Burden of Disease project estimates that vitamin A deficiency increases the risk of diarrhea, measles, and lower respiratory tract infections.4 In 2017, an estimated 233,000 global deaths were linked to this increased risk.5

Impact of vaccine-preventable diseases

Worldwide, at least 15% infants did not receive all recommended childhood vaccines.6 In Nigeria, where New Incentives operates, 43% of infants did not receive all recommended vaccines.7

Impact of parasitic worms

Many types of parasitic worms infect human beings, causing illnesses including schistosomiasis and soil-transmitted helminthiasis. Hundreds of millions of people have these infections.8

Global incomes

According to Our World in Data’s analysis of the World Bank’s PovcalNet data, about 65% of the world’s population in 2015 had per capita consumption less than $10 per day (or $3,650 per year).9

Sources

Document Source
GBD 2017 Risk Factor Collaborators, 2018 Source (archive)
GiveWell's non-verbatim summary of a conversation with the Institute for Health Metrics and Evaluation, April 5, 2019 Source
Institute for Health Metrics and Evaluation, Global Burden of Disease, GBD Compare, Global ascariasis prevalence Source (archive)
Institute for Health Metrics and Evaluation, Global Burden of Disease, GBD Compare, Global hookworm disease prevalence Source (archive)
Institute for Health Metrics and Evaluation, Global Burden of Disease, GBD Compare, Global malaria deaths Source (archive)
Institute for Health Metrics and Evaluation, Global Burden of Disease, GBD Compare, Global schistosomiasis prevalence Source (archive)
Institute for Health Metrics and Evaluation, Global Burden of Disease, GBD Compare, Global trichuriasis prevalence Source (archive)
Our World in Data, Global vaccination coverage, Nigeria, 2019 Source (archive)
Our World in Data, Global vaccination coverage, World, 2019 Source (archive)
Rosen and Ortiz-Ospina, 2019 Source (archive)
UNICEF, "Immunization," 2020 Source (archive)
WHO, World Malaria Report 2019 Source (archive)