Survivorship Bias

Surface

During World War II, statistician Abraham Wald was asked to analyze bullet holes in returning aircraft to determine where to add armor. His insight: the holes showed where planes could be hit and survive. The places with no holes were where the planes that didn't return had been hit. The military had been about to armor the wrong places.

Middle

Survivorship bias is the logical error of focusing on things that passed a selection process while overlooking those that did not. We hear about successful startups, not the thousands that failed with identical strategies. We read biographies of exceptional people and extract lessons that may have been irrelevant to their success.

Deep

Every field of human endeavor is distorted by survivorship bias. Success literature is written by survivors. History is written by winners. Medical case studies feature recoveries. The result is a systematically skewed picture of what actually works. The most important data is almost always the data you cannot see.