A popular way to raise money for charity in the U.K. is to undertake a sponsored skydive. Every year, thousands of people gather donations for good causes and then throw themselves out of planes. This may sound like a win-win scenario: The fundraiser offers an exhilarating once-in-a-lifetime experience, and at the same time raises money for a good cause. What could be the harm in that?

A study of two popular parachuting centers in Perthshire, Scotland, my home country, found that over five years (1991 to 1995), approximately 1,500 people went skydiving for charity. Collectively they raised more than £120,000 (about £200,000 today, or more than $300,000), which seems pretty impressive. But the whole venture was badly misguided.

First, the cost of diving had to come out of the sponsored donations: Of the £120,000 raised, only £45,000 ultimately went to the charities. Second, and even more important, the skydivers were mostly first-time jumpers. They received only six hours of training before the jump, and around a third wore unsuitable footwear. The result? First-time jumpers had 163 injuries, 103 of the injuries skydivers received required hospitalization, and the average hospital stay was nine days.

The cost of all these injuries to the U.K.’s National Health Service was around £610,000. That means that, every £1 raised for the charities, which ironically were mostly health-related, cost the NHS about £13. Despite evidence of the negative impact of sponsored skydives, the practice is still popular.

The Scottish skydiver example is extreme, but ineffective altruism is far too common. Even though some charities are exceptional at turning resources into improvement in people’s wellbeing, many have no more than negligible effect, and a few are even actively harmful. Yet ineffective charities still get funding. Why?

The skydivers provide us with a clue: Performing stunts for charity appeals to us emotionally. It’s unusual, it’s exciting, and it’s instinctively pleasing for donations to be “earned” through risk-taking. The problem, as the study shows, is that in the cold light of day, these emotional reactions can turn out to be entirely misleading.

Charities often appeal to our sympathies by using images of sick children and cute pandas, rather than facts and figures that prove their impact. Yet we fund them anyway. Psychologists and economists have shown that a major motivation for doing good is the “warm glow” it gives us, rather than any rational assessment of the effects. Inevitably, this emotional basis for altruism distorts our ability to think clearly about helping others.

In one study, participants were asked how much they would be willing to pay in order to save migrating birds from drowning as a result of an oil spill. Some were told that 2,000 birds would die without their donation; others were told 20,000, and a third group 200,000. The number of birds saved had almost no impact on the amount people would give, about $80 in each case. People responded to the image of a single bird, exhausted, with oil-soaked feathers.

Why do our brains respond like this? In the world in which we evolved, the number of people impacted by our actions was small, and the area in which we could help was localized. We could see the results of our actions, so responding on the basis of our emotions worked pretty well. But now we live in a world in which thousands of people can be affected by our actions, including people far away who we will never meet, and who we will never know as anything other than statistics. The emotional part of our brains cannot truly comprehend this. As a result, our sympathetic instincts can lead us badly astray.

To make matters worse, because we don’t respond to figures, charities often don’t give us their figures. When we make a donation, we almost never find out what happened to that money. However well or poorly the charity does, we get the same positive feedback: glossy leaflets touting the charity’s success. We feel good either way.

If we really want to do good, we need to focus on our ability to reason—to examine and respond to evidence—in order to channel our sympathies in the right direction. We should do whatever helps others the most, rather than fixating on any particular way because of its emotional appeal. I call this approach effective altruism.

How can we put this into practice? By seeking out charities with an excellent track record (or which are trialing something new and promising). Look at their success figures, compare different organizations, and make a reasoned, impact-based decision. And if that sounds like a lot of work, you can always get a little help: organizations like GiveWell publish their research into the most effective charities in the world, through which your donations can significantly improve the lives of thousands of people. The tools are out there to find the best, most effective charities in the world. When it comes to giving, the question is: Are you willing to put in the effort?

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