May's theorem

Condorcet methods Positional voting Cardinal voting Quota-remainder methods Approval-based committees Fractional social choice Semi-proportional representation By ballot type Pathological response Strategic voting Paradoxes of majority rule Positive results In social choice theory, May's theorem, also called the general possibility theorem,[1] says that majority vote is the unique ranked social choice function between two candidates that satisfies the following criteria: The theorem was first published by Kenneth May in 1952.

Another way of explaining the fact that simple majority voting can successfully deal with at most two alternatives is to cite Nakamura's theorem.

The Nakamura number of simple majority voting is 3, except in the case of four voters.

[citation needed] Let A and B be two possible choices, often called alternatives or candidates.

Define a social choice function called simple majority voting as follows:[1] May's theorem states that simple majority voting is the unique social welfare function satisfying all three of the following conditions:[1]