Arrow’s (im)possibility theorem

International audienceArrow’s (im)possibility theorem is one of the most famous and important contri-butions in economics. It concerns the difficulty to aggregate a set of individualpreferences, given as rankings of a set of available alternatives, into a unique socialpreferences ranking via a social welfare function, or into a unique social choice.Arrow proves that in a specific framework, it is impossible to find a social welfarefunction which simultaneously satisfies four conditions: universal domain, weakPareto principle, independence of irrelevant alternatives, and no dictator. Our no-tice presents this theorem, one of its proofs, and, we hope, invites the reader todiscover social choice theor