Vote unitarity: Difference between revisions
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3.) Unitary Transformations: A voter's total vote weight cannot be created or destroyed but may be spent to elect winners who represent them through the rounds of tabulation, winner selection, and reweighting. The amount of remaining vote weight available to be used by any voter at any stage in the tabulation must always be their initial vote weight minus the amount they have spent. A voter who has achieved full representation by electing their favorite will have no vote weight left in play in subsequent rounds unless their favorite candidate received a surplus of votes and didn't need the full weight of their supporters votes to be elected.
== Rationale and Critique ==
When [[Single Transferable Vote]] allocates entire voters to winners it can violate vote unitarity by over removing influence in some cases. This occurs in all allocation systems; for example in [[Allocated Score]] somebody who only gave a score of 1 to the winner could lose all future influence. [[Reweighted Range Voting]] on the other hand only reduces influence fractionally, so a voter who got a candidate they gave max score in the first round would only have their ballot weight reduced to 1/2.
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This rational became the foundation of a new class of Unitary Proportional voting methods which were invented to satisfy Vote Unitarity and Hare Proportionality, including [[Sequentially Spent Score|Sequentially Spent Score Voting]].
The principle of proportionate spending can also be critiqued in that it increases strategic incentives. Note that "proportionate spending" only refers to how a ballot is reweighted ''after'' a candidate is elected. This leaves open the question of how much power a vote has to elect a candidate in the first place. Thus, there are two possibilities.
# If a rating of (for example) 3 out of 5 has only 3/5 the power (or less) to elect a candidate in the first place, then the strategic incentive is to give higher ratings to your favorite among the most borderline-viable candidates, in order to get that candidate elected.
# Following the same example, if a rating of 3 out of 5 has more than 3/5 the power to elect a candidate in the first place, the strategic incentive is to give lower ratings, so that the amount of your ballot that is used up when a candidate is elected is less than the voting power you exerted in electing them.
This leads some voting theorists, such as Jameson Quinn, to consider vote unitarity an actively harmful criterion.
== Compliant Voting Methods ==
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