Robust voting

The formal equivalence between social choice and statistical estimation means that criteria used to evaluate estimators can be interpreted as features of voting rules. The robustness of an estimator means, in the context of social choice, insensitivity to departures from majority opinion. In this paper we consider the implications of substituting the median, a robust, high breakdown estimator, for Borda's mean. The robustness of the median makes the ranking method insensitive to outliers and reflect majority opinion. Among all methods that satisfy a majority condition, median ranks is the unique one that is monotonic. It is an attractive voting method when the goal is the collective assessment of the merits of alternatives.