Monotonicity paradoxes in the theory of elections

Abstract An election procedure based on voter preference rankings is said to be monotonic if the alternative chosen by the procedure for any profile of voter preference rankings is also chosen after it is moved up in one or more of the profile's rankings. Several reasonable-sounding election procedures that are known to violate monotonicity are examined along with some new classes of non-monotonic procedures. Closely-related procedures that are monotonic are also identified. The procedural mechanisms and combinatorial structures that give rise to failures of monotonicity are analyzed in some detail.