Vote unitarity: Difference between revisions

Since [[Single Transferable Vote]] allocates voters it violates 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. This violates the principle of one person one vote since this person would essentially be allowed to vote with half weight in later rounds. Proponents of [[Single Transferable Vote]] would use this argument for its superior fairness over [[Reweighted Range Voting]] and the [[Reweighted Range Voting]] use the opposite argument. Since [[Reweighted Range Voting]] and [[Single Transferable Vote]] are very popular systems which violate Vote Unitarity in opposite ways it should be possible to find a balanced middle ground.

On an even further extreme, [[Bloc voting]] when treated as a sequential method often violate Vote Unitarity even more than [[Reweighted Range Voting]] since a voter can fully influence the election of multiple candidates independently without any reweighing. [[Cumulative voting | Cumulative Voting]] attempts to mitigate this by giving voters the same amount of vote beforehand with the understanding that it is up to them to chose how to reweight on their ballot. This also has the added effect that makes outcome of [[Cumulative voting | Cumulative Voting]] have higher [[Proportional representation]] than standard Bloc Systems. Thiele methods such as [[Reweighted Range Voting]] violate Vote Unitarity less than Bloc elections because they at least reduce ballot weight to some degree. In addition they do this reweigting in such a way to satisfy the Hare Quota Criterion.

[[Keith Edmonds]] saw a unification of [[Proportional representation]] and the concept of one person one vote. He coined the term "Vote Unitarity" for the second concept and designed a score reweighting system which satisfied both Hare Quota Criterion and Vote Unitarity. As such it would preserve the amount of score used through sequential rounds which attributing representation in a partitioned way. It would assigne Hare Quotas of score to winners which allowed for a voters influence to be spread over multiple winners. The final system was originally proposed in a late stage of the [[W: 2018 British Columbia electoral reform referendum]] but was not selected for the referendum ballot. This system, [[Sequentially Spent Score]], was the first sequential [[Multi-Member System | Multi-Winner]] [[Cardinal voting systems | Cardinal voting system]] built on [[Score voting]] ballots to satisfy Vote Unitarity. Variants were soon found.