Maskin monotonicity is a desired property of voting systems, suggested by Eric Maskin. Each voter reports his entire preference relation over the set of alternatives. The set of reports is called a preference profile. A social choice rule maps the preference profile to the selected alternative. For a preference profile with a chosen alternative , there is another preference profile such that the position of relative to each of the other alternatives either improves or stays the same as in . With Maskin monotonicity, should still be chosen at .