Season 5, Episode 2: A vote between three people to be commander of the Night’s Watch is occurring. When there are three or more choices, Kenneth Arrow showed in his impossibility theorem that all three of these cannot occur: * If every voter prefers alternative X over alternative Y, then the group prefers X over Y. * If every voter’s preference between X and Y remains unchanged, then the group’s preference between X and Y will also remain unchanged (even if voters’ preferences between other pairs like X and Z, Y and Z, or Z and W change). * There is no “dictator”: no single voter possesses the power to always determine the group’s preference. The take-home message – different voting schemes could easily you different results!
