Will Rogers Phenomenon

Moving a below-average member from one group to another can raise the average of both groups simultaneously — a statistical illusion that can make deteriorating situations look like improvements.

• Will Rogers' joke: when the Okies left Oklahoma for California, they raised the average IQ of both states.
• A hospital that transfers its sickest patients to a specialist center improves its own survival statistics and can also improve the specialist center's (by adding patients who are less critical than the existing average).
• A football team that trades its worst player to a team with an even weaker roster raises the average quality of both squads.