Will Rogers Effect
The consequence of moving an element from one set to another set which raises the average values of both sets.
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Origin
Named after a quip attributed to Will Rogers — "When the Okies left Oklahoma and moved to California, they raised the average intelligence level in both states." Epidemiologist Alvan Feinstein and colleagues at Yale formally applied the idea in a 1985 New England Journal of Medicine paper, showing that improved diagnostic imaging was reclassifying lung-cancer patients into higher stages — making survival rates appear to rise in every group without any actual change in outcomes.
Updated February 22, 2026