Range Voting - Properties

Properties

Range voting allows voters to express preferences of varying strengths.

Range voting satisfies the monotonicity criterion, i.e. raising your vote's score for a candidate can never hurt their chances of winning, and lowering it can never help their chances. Also, in range voting, casting a sincere vote can never result in a worse election winner (from your point of view) than if you had simply abstained from voting. Range voting passes the favorite betrayal criterion, meaning that it never gives voters an incentive to rate their favorite candidate lower than a candidate they like less. Range voting advocates contend that this is a good property, because it leads to higher average voter satisfaction when voters are honest, and still gives voters the choice to strategically lower their scores for less preferred candidates if they choose.

Range voting is independent of clones in the sense that if there is a set of candidates such that every voter gives the same rating to every candidate in this set, then the probability that the winner is in this set is independent of how many candidates are in the set.

In summary, range voting satisfies the monotonicity criterion, the favorite betrayal criterion, the participation criterion, the consistency criterion, independence of irrelevant alternatives, resolvability criterion, and reversal symmetry. It is immune to cloning, except for the obvious specific case in which a candidate with clones ties, instead of achieving a unique win. It does not satisfy either the Condorcet criterion (i.e. is not a Condorcet method) or the Condorcet loser criterion, although with all-strategic voters and perfect information the Condorcet winner is a Nash equilibrium. It does not satisfy the majority criterion, but it satisfies a weakened form of it: a majority can force their choice to win, although they might not exercise that capability. It does not satisfy the later-no-harm criterion, meaning that giving a positive rating to a less preferred candidate can cause a more preferred candidate to lose.

As it satisfies the criteria of a deterministic voting system, with non-imposition, non-dictatorship, monotonicity, and independence of irrelevant alternatives, it may appear that it violates Arrow's impossibility theorem. The reason that range voting is not regarded as a counter-example to Arrow's theorem is that it is a cardinal voting system, while the "universality" criterion of Arrow's theorem effectively restricts that result to ordinal voting systems.