Survivorship Bias: A Lesson from History
We often cling to our beliefs because we trust the evidence without question. But why should we consider an alternative viewpoint? The story of Abraham Wald offers a powerful example of the importance of challenging the obvious and questioning our assumptions. By examining the overlooked details and understanding the concept of survivorship bias, Wald's insights during World War II not only saved countless lives but also provided a timeless lesson in critical thinking and data analysis. So let’s dig down and take a look into the life and findings of Wald to find out more…
Born in 1902, Wald was a mathematician who fled Nazi persecution and moved to the USA, where he joined Yale. During World War II, he became part of the Statistical Research Group (SRG) at Columbia University, working on military problems.
One major issue for the department was reducing downed aircraft. The military mapped bullet damage on returning planes, noticing most hits were on the wings and tail. The high command's solution? Reinforce those areas.
Enter Wald. His surprising advice: don’t armour the wings and tail, armour the engine. Why? Wald recognised survivorship bias. The military were only analysing planes that returned, not those which had been shot down. The bullet holes showed where planes could take damage and still fly home.
Wald's math-trained mind asked, "What assumptions are you making? Are they justified?" The officers assumed the returning planes were a random sample of all planes - an incorrect assumption.
Wald's insight saved countless lives, proving the importance of questioning assumptions. His story is a prime example of survivorship bias, a cognitive bias where we focus on the successful outcomes (survivors) while overlooking the failures (those that did not survive). This bias can lead to erroneous conclusions if we fail to consider all data, including the missing pieces.
To illustrate the impact of Wald's work, consider this: during World War II, the average survival rate of aircraft increased significantly after implementing Wald's recommendations. By analysing the patterns of bullet holes and understanding where the critical vulnerabilities were, the military could make more informed decisions that directly contributed to saving lives.
Tragically, in 1950, Wald and his wife died in a plane crash during a trip to India. His legacy, however, lives on, teaching us the importance of critical thinking and the dangers of survivorship bias.
We often focus solely on success stories, ignoring failures. Yet, as Henry Ford said, "Those who never make mistakes work for those of us who do." Wald’s story reminds us to challenge the obvious, question our assumptions, and learn from our mistakes.
In a world that celebrates success, let's not forget the value of failures and the lessons they offer. Wald's story teaches us that sometimes, the greatest insights come from looking where no one else does. By acknowledging and understanding survivorship bias, we can make better, more informed decisions in all aspects of life.
