Impossibility Theorems with Interpersonally Comparable Welfare Levels: The “Extended Sympathy Approach” Reconsidered

We re-examine a type of interpersonal welfare comparison, called the “extended sympathy” approach, which Arrow (1977), Hammond (1976) and Roberts (1980a) introduced in order to escape from Arrovian impossibility theorems. In particular, we extend the positional dictatorship theorem due to Roberts to the case where the domain of social choice rules satisfies the axiom of identity. We show that there is a positional dictator if the rule with the domain satisfies independence, Suppes unanimity and monotonicity JEL Classification Numbers: 022, 025, 026