The Legend of Abraham Wald
Casselman examines the popular story in which Abraham Wald told the military to armour the parts of returning aircraft that showed few hits. He argues that the story is largely a plausible reconstruction with little documentary support. The reliable sources he finds are two vague mentions in W. Allen Wallis's memoir, which do not name Wald, and Wald's own technical memoranda. Those memoranda contain no armour recommendations and concern estimating survival probabilities and aircraft vulnerability from data on returning planes. In a postscript Casselman concedes that Wallis later credited Wald explicitly with survivorship reasoning, so his earlier criticism of the internet versions was overstated.
Casselman examines the popular story in which Abraham Wald told the military to armour the parts of returning aircraft that showed few hits. He argues that the story is largely a plausible reconstruction with little documentary support. The reliable sources he finds are two vague mentions in W. Allen Wallis's memoir, which do not name Wald, and Wald's own technical memoranda. Those memoranda contain no armour recommendations and concern estimating survival probabilities and aircraft vulnerability from data on returning planes. In a postscript Casselman concedes that Wallis later credited Wald explicitly with survivorship reasoning, so his earlier criticism of the internet versions was overstated.
Written from the the column itself, American Mathematical Society feature column, read 2026-10-23.
What our sources record
Recorded when this source was checked, figures included, with page references and quotation marks removed.
June 2016. https://www.ams.org/samplings/feature-column/fc-2016-06