Understanding Arrow's impossibility theorem Arrow's impossibility theorem states that under certain assumptions about preferences, no voting system exists which satisfies all of the following properties: Unanimity Transitivity Independence of Irrelevant Alternatives No dictators Assume individuals in a society have preferences regarding the following possible outcomes: A, B, and C For each description in the following table, identify the property of a desirable voting system it portrays. Independence of Irrelevant Alternatives No Description Unanimity Transitivity Dictators If A beats C, and C beats B, then A beats B. The ranking between B and A does not depend on whether C is also available. There is no person who always gets what he wants, despite everyone else's preferences If everyone prefers A to C, then A beats C
