ABSTRACT
Building on the previous chapter, the current chapter describes six fairness criteria and argues that they should be satisfied by any reasonable voting method. Instances are provided of voting methods that always satisfy a particular criterion as well as examples where voting methods fail to satisfy a particular criterion. Each of the preferential voting schemes presented in Chapter 17 is seen to violate at least one of the six fairness criteria. Naturally this leads to the search for an “ideal” voting method-one that satisfies all the fairness criteria. More broadly, we hope to identify a social ranking method (for collective decision making) that satisfies all of these fairness criteria. In a truly ingenious demonstration, Kenneth Arrow showed mathematically that it is impossible to have a social ranking method that meets all the fairness criteria. Consequently, we must consider the strengths and weaknesses of each social ranking method in order to identify one that best meets our needs. This chapter also introduces the idea of insincere voting, in which voters can purposely misrepresent their voting preferences in order to gain at the expense of other voters in the system.
