[This is the fifth post in a brief series explaining the current GiveWell top charities. You can get all the information in this post on GiveWell’s website, but my blog post is both shorter and less boring.]
GiveWell’s top charities list includes four deworming charities: Sightsavers, the END Fund, the Deworm the World Initiative, and the Schistosomiasis Control Initiative. I’m combining them into one post because a lot of the stuff I can say about them is the same.
The most important thing to know about deworming charities is that they are NOT HEALTH CHARITIES. Deworming charities are economic development charities. You might think they are health charities, because they give pills to people in order to treat their diseases, and that is a thing one generally does if one is a health charity. If one is an economic development charity, one gives people cows or job training or money or something. But in fact that is just the deworming charities’ very clever disguise.
Deworming works in the sense that if you have worms, and take the pills, you won’t have worms anymore. But the effects of being dewormed on health are very small. Having worms generally doesn’t kill you, and it’s rare for people to get very sick because they have worms. A lot of meta-analyses find very small or no effect of deworming on things like weight, height, anemia, school performance, or cognition.
So that might lead you to ask why there are four (four!) GiveWell top charities that deworm people if it doesn’t make people healthier. The answer is that it is possible– but by no means certain– that deworming has an effect on children’s long-term development that causes them to earn more income.
Miguel and Kremer (2004) found that deworming leads to a 25% decrease in school absenteeism. The ten-year followup finds that people who were dewormed as children work more, earn more, are more likely to work in the high-earning manufacturing sector, eat more meals, and have better self-reported health. GiveWell has seen a preliminary 15-year followup that shows similar results.
There are lots of reasons to be uncertain about this study. It’s only one study, and there might be alternate explanations for the findings, or there might have been publication bias. There was a lot of flooding in the study area, so people were more likely to have worms than if there was less flooding. Some researchers argue that Miguel and Kremer (2004) and the followup are at risk of significant methodological bias. (Others disagree, including David Roodman, who reanalyzed the studies for GiveWell.)
The big advantage of deworming is that it is very very cheap. A person can be dewormed for less than a dollar. If you take the ten-year followup seriously, the annualized rate of return on deworming is 32%— that is, for every dollar invested in deworming, you earn 32 cents back every year, presumably until the beneficiaries die or retire. If there’s even a five percent chance that deworming works as advertised, it’s a good investment. Under any reasonable estimate of the likelihood that deworming works, it’s one of the most cost-effective interventions for making people richer.
The primary negative impact of deworming is side effects from the medications: deworming medications have unpleasant side effects, including headache, nausea, upset stomach, vomiting, abdominal pain, and fever. Deworming programs may also interfere with the provision of routine health care services because all the nurses are temporarily busy giving deworming medicine instead. The relationship between deworming treatment and malaria is complex and poorly understood, but it may be that deworming causes children to have a higher density of malaria parasites in their blood.
I have prepared the following table to help you choose which deworming charity to donate to:
| Name | Program | Room for more funding (in millions of dollars) | Kinda sketchy? | Coverage rate | Open questions |
| Deworm The World | Advocacy; monitoring/evaluation; technical assistance; funding | $27 | No | 80-90% | None |
| Schistosomiasias Control Initiative | Advocacy; funding/ drug donations; monitoring/evaluation; technical assistance | $16.9 | Yes | 80-90% | Will SCI use additional funding to treat adults instead of children? How accurate are SCI’s coverage surveys? |
| END Fund | Filling funding gaps in other orgs; technical assistance | $45.8 | Limited track record | 50-60% | Do their programs reach a high percentage of children targeted? How much money will they raise from other funders? Will GiveWell-directed donations increase the amount they budget for deworming? |
| Sightsavers | Technical assistance; funding | $1.6 | Limited track record | 58-99% | Limited track record for implementing deworming. Spends a lot on fundraising. Will GiveWell-directed donations increase the amount they budget for deworming? |
Why might you donate to deworming?
- You like high-risk high-reward bets, and AI risk is just too fashionable.
- You want to increase people’s income in a very cost-effective way, even if it might not work.
- You care more about increasing incomes and economic development than you do about improved health outcomes or preventing the death of children.
- In a war between epidemiologists and economists you are on Team Economist.
- You have a phobia of parasitic worms.
Thing of Things 
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Typo note: In this and the AMA post, the header says they’re the “first post” in the series, rather than their actual position in the series.
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Errrrrr make that AMF. Stupid lexicalized initialisms…
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What is sketchy about SCI?
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Wait, schistosomes don’t cause measurable health impacts? I remember they were covered in my Parisitology course and I seem to remember coming away with the impression schistosomiasis was a pretty bad disease? But I could be remembering wrong or something.
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“If there’s even a five percent chance that deworming works as advertised, it’s a good investment.”
That doesn’t fit with the 32% return figure. A five percent chance of 32% return (and ninety five percent chance of 0% return) gives an expected return of 1.6%, but you can get an expected return of around 7% by investing in the stock market (and thus do more good than deworming by investing now and Giving Directly in the future).
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Unless worms have some kind of cognitive or doing-stuff-impairing effects I would expect the economic effect of deworming (as compared to the economic effects of other health interventions) to be in line with how bad worms are compared to other health problems. This makes me wonder if similar studies of economic impact have in fact been done about other health interventions – if no, then the focus on deworming seems to be a consequence of what someone happened to do a study on; if yes, and the results were much less encouraging, then (again unless worms have some long-term cognitive or otherwise impairing effect) I would be really surprised if this deworming finding held up.
Put a different way, has anyone checked whether anti-malaria interventions have similar economic effects? If we’re looking at long-run follow-on effects from interventions, we should also be including those effects when evaluating/comparing anti-malaria interventions that are typically primarily evaluated in terms of lifesavingness.
(admittedly I am pretty unfamiliar with the literature in this area and my hypothetical objections may be completely unfounded)
Thanks for mentioning the side effects of the treatments. In addition to the above concerns, I’m not quite comfortable causing those effects for an uncertain benefit, at least not when the other GiveWell-evaluated interventions exist as alternatives.
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