During World War II, a group of experts was assembled and tasked with finding ways of reducing the number of bomber aircraft that didn’t return from their missions.
The experts began by studying bullet hole patterns from the aircraft that had made it back. They decided the solution was to reinforce the areas hit the most with additional armor. This included the fuselage, the fuel systems, and a number of additional areas throughout the aircraft. Pretty much everywhere but the engines, noting the engines had the least number of bullet holes per square foot.
One expert disagreed. His name was Abraham Wald. Wald inverted the problem and asked what seemed like a simple question: Where were the missing bullet holes? The bullet holes that would have been all over the engines if the hits were evenly distributed.
These “missing” bullet holes where on the bomber aircraft that didn’t return. The ones shot down. Wald surmised the most vulnerable parts of the aircraft weren’t where all the bullet holes were on the bomber aircraft that made it back.
The solution was to reinforce areas where the bullet holes “weren’t”; because that’s where the bullet holes would have been on the bomber aircraft that were shot down.
“Invert, always invert: Turn a situation or problem upside down. Look at it backward. What happens if all our plans go wrong? Where don’t we want to go, and how do you get there? Instead of looking for success, make a list of how to fail instead — through sloth, envy, resentment, self-pity, entitlement, all the mental habits of self-defeat. Avoid these qualities and you will succeed.” — Charlie Munger