Survivorship Bias

In WWII, aircraft returning from bombing missions often sustained heavy damage from enemy fire. The distribution of holes in the fuselage and wings might look something like this:

Imagine you're a WWII-era statistician tasked with assessing the damage of returning airplanes. Which parts of the plane depicted above should you reinforce?

If your answer was the areas with the most bullet holes, you'd be wrong.

Abraham Wald, working with the Statistical Research Group at Columbia University, pointed out that this is a classic example of survivorship bias: Returning aircraft demonstrated where the planes could sustain damage. The additional armor actually needed to go where there weren't bullet holes, because the planes that got hit there never came back.

When we examine our history, it's tempting to look at only the success stories. But the people, societies, and organizations that didn't survive have important stories to tell us as well.

Sometimes, those quiet stories about the ones that didn't succeed have more to tell us than the ones that did.