AP MicroeconomicsGame Theory & Information
Arrow's Impossibility Theorem
Arrow's impossibility theorem proves no ranked voting system can convert individual preferences into a group ranking while satisfying a few basic fairness conditions and avoiding a dictator.
Kenneth Arrow showed that with three or more options, no voting rule can simultaneously guarantee unrestricted domain, Pareto efficiency, independence of irrelevant alternatives, and non-dictatorship. Any system that meets the other criteria must effectively let one voter dictate the outcome. The result is a cornerstone of social choice and public choice theory and generalizes the Condorcet paradox.