Scale invariance

Scale invariance can refer to one of two criteria: a cardinal voting method criterion and an ordinal one.

Multiplying every ballot's score of every candidate by a constant ${\displaystyle \alpha>0}$ should not change the outcome.

The ordinal method criterion is also called the homogeneity criterion. It is:

For every way of ranking the candidates, multiplying the number of voters who express this preference by a constant ${\displaystyle \alpha>0}$ should not change the outcome.

Strong variant, for cardinal method is:

Multiplying one or more ballot's score of every candidate by a constant ${\displaystyle \alpha>0}$ should not change the outcome.

These criteria represent a desideratum that the method should not rely on absolute numbers when selecting a winner, just on the candidates' or factions' relative support.