Benjamin Todd

The y-axis shows the amount of ill health in the population, measured in disability-adjusted life years, or dailies, per 100,000 people.

where one daily equals one year of life lost due to ill health.

The x-axis shows the number of doctors per 100,000 people.

Here's a graph titled dailies per 100,000 people versus doctors per 100,000 people.

Looking at the graph, we notice that as the number of doctors increases, the dailies gained drops off pretty rapidly.

Much of the gains seem to come from the initial 100 doctors per 100,000 people.

you can see that the curve goes nearly flat once you have more than 150 doctors per 100,000 people.

After this point, which almost all developed countries meet, additional doctors only achieve a small impact on average.

So, if you become a doctor in a rich country like the US or UK, you may well do more good than you would in many other jobs, and if you're an exceptional doctor then you'll have a bigger impact than these averages, but it probably won't be a huge impact.

In fact, in the next chapter we'll show how almost any college graduate can do more to save lives than a typical doctor.

and in the rest of the career guide, will cover many other examples of common but ineffective attempts to do good.

These findings motivated Greg to switch from clinical medicine into biosecurity, for reasons we'll explain over the rest of the guide.

Despite this uninspiring statistic about how many lives a doctor saves, some doctors have had much more impact than this.

Let's look at some examples from the highest-impact careers in history and see what we might learn from them.

First, let's turn to medical research.

By 1968, it had been shown that a solution of glucose and salt administered via a feeding tube or intravenous drip could prevent death due to cholera.

But millions of people were still dying every year from the disease.

While working in a refugee camp on the border of Bangladesh and Burma, Dr. David Nyland sought to turn this insight into a therapy that could be used in poor rural areas.

He showed in a study that simply drinking a solution made at the right concentration and consumed at the right rate could be almost as effective as delivery via feeding tube or IV.

This meant the treatment could be delivered with no equipment and using extremely cheap and widely available ingredients.