BibliographyDefinition 2.6 (Equal score difference). A domain P satisfies the equal score difference (ESD) condition with respect to s if, for all x, y ∈ X, either all orderings in P agree on {x, y}, or if not, thenfor all , ∈ P such that | {x,y} = | {x,y} .Note that for the Borda count the latter condition reduces tofor all , ∈ P such that | {x,y} = | {x,y} , which we will also refer to as the equal rank difference (ERD) condition.Theorem 2.1. A domain is Arrovian for the proper scoring method F s if and only if it satisfies the equal score difference condition with respect to s.Proof. Clearly, any scoring method is non-dictatorial and satisfies the Pareto rule on any domain. Let P satisfy the equal score difference condition. In order to verify IIA consider * 11