Factfulness: Ten Reasons We're Wrong About the World – and Why Things Are Better Than You Think

The 80/20 Rule
It’s so easy to get things out of proportion, but luckily there are also some
easy solutions. Whenever I have to compare lots of numbers and work out
which are the most important, I use the simplest-ever thinking tool. I look for
the largest numbers.

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That is all there is to the 80/20 rule. We tend to assume that all items on a
list are equally important, but usually just a few of them are more important
than all the others put together. Whether it is causes of death or items in a
budget, I simply focus first on understanding those that make up 80 percent of
the total. Before I spend time on the smaller ones, I ask myself: Where are the
80 percent? Why are these so big? What are the implications?
For example, here’s a list of the world’s energy sources, in alphabetical
order: biofuels, coal, gas, geothermal, hydro, nuclear, oil, solar, wind.
Presented like that, they all seem equally important. If we instead sort them
according to how many units of energy they generate for humanity, three
outnumber all the rest, as this graph shows.
To give myself the big picture I would use the 80/20 rule, which tells us
that oil+coal+gas give us more than 80 percent of our energy: 87 percent in
fact.
I first discovered how useful the 80/20 rule is when I started to review aid
projects for the Swedish government. In most budgets, around 20 percent of
the lines sum up to more than 80 percent of the total. You can save a lot of
money by making sure you understand these lines first.
Doing just that is how I discovered that half the aid budget of a small health
center in rural Vietnam was about to be spent on 2,000 of the wrong kind of
surgical knives. It’s how I discovered that 100 times too much—4 million
liters—of baby formula was about to be sent to a refugee camp in Algeria.
And it is how I stopped 20,000 testicular prostheses from being sent to a small

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youth clinic in Nicaragua. In each case I simply looked for the biggest single
items taking up 80 percent of the budget, then dug down into any that seemed
unusual. In each case the problem was due to a simple confusion or tiny error
such as a missing decimal point.
The 80/20 rule is as easy as it seems. You just have to remember to use it.
Here’s one more example.