A vote-buying mechanism is such that each agent buys a quantity of votes x to cast for an alternative of her choosing, at a cost c(x), and the outcome is determined by the total number of votes cast for each alternative. In the context of binary decisions, we prove that the choice rules that can...

Consider the following principle regarding the performance of collective choice rules. "If a rule selects alternative x in situation 1, and alternative y in situation 2, there must be an alternative z, and some member of society whose appreciation of z relative to x has increased when going from...