Outcome error

Outcome error is the difference between what voters want and what they actually get. It can apply to individuals (what one person wanted vs. what they got) as well as being summed all participants in an election. The latter gives an idea of how well the voting system serves as a way of determining how well any given voting system serves the votership in any given circumstance.

Note that "want" is much more than just "I want Option X to win". Most voters have some idea of not only what outcome they'd most prefer, but also a range of other outcomes which would be acceptable, others which would be tolerable, and still others which would be bad or even absolutely unacceptable. In the event that Option X does win the election, the degree of individual outcome error goes up as we move from "preferred" to "absolutely unacceptable".

Range voting alone allows an unambiguous expression of this complexity for each of the possible options, allowing compromise so that (e.g.) an option that most people agree is tolerable could prevail, despite violent disagreement about which option would be best.