During World War II, faced with shocking bomber losses over Europe, Allied analysts went looking for a fix. They studied the aircraft that limped back to base, mapped out the bullet holes across their wings, fuselages and tails, and reached an obvious conclusion: add armor where the planes had the most damage. Abraham Wald, a Hungarian-born statistician asked to weigh in, said that was neat, but completely wrong. The damage they could see was damage a bomber could survive. It was actually the