Arrow’s Theorem

The Axioms for a fair voting system (eg. Political Election) :

1. Non-dictatorship:
◇ Outcome decided not by one ‘dictator’, but more than one person.

2. Unanimity
◇ If everyone votes that A is better than B, then A will be ranked higher than B in the final result.

3. Independence of irrelevant alternatives
◇ The ranking of A relative to B should not be affected by someone changing their mind about C.

Arrow’s Theorem says that if there are more than 2 people (parties) to vote for, then there is no fair voting system.

Most democratic voting systems violate the 3rd axiom (independence of irrelevant alternatives).


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