Monotonicity

The monotonicity is a Voting Theory criterion/principle that characterizes voting methods for choosing the winner.


Monotonicity is satisfied when:

  • if
    • an alternative $x$ rises or does not fall in the individual ordering and
    • $x$ was preferred to another alternative $y$ before the change in the individual orderings
  • then
    • (1) $x$ should still remain at least at the same position
    • (2) if $x$ is a winner, it should remain the winner
    • (note that (1) $\Rightarrow$ (2))


Theorems

This principle is used in two important Voting Theory theorems:


Methods

Methods that respect Monotonicity:

Methods that don't respect Monotonicity


Sources

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