Multi-member system

From Electowiki
(Redirected from Multi-winner method)
Jump to navigation Jump to search

Multi member voting methods, also called multi winner methods, are voting methods which elect multiple people in one election. It is common for several of these voting methods to be combined into a Regional System.

Bloc Voting Methods[edit | edit source]

Bloc methods find the candidate set with the most support or the most votes overall using the same metric which would be used in a single member system. The number of seats up for election is determined and the top candidates are elected to fill those seats.

Common examples:

  • Bloc Approval Voting: Each voter chooses (no ranking) as many candidates as desired. Only one vote is allowed per candidate. Voters may not vote more than once for any one candidate. Add all the votes. Elect the candidates with the most votes until all positions are filled.
  • Bloc Score Voting: Each voter scores all the candidates on a scale with three or more units. Starting the scale at zero is preferable. Add all the scores. Elect the candidates with the highest total score until all positions are filled.
  • Bloc STAR Voting: Each voter scores all the candidates on a scale from 0–5. All the scores are added and the two highest scoring candidates advance to an automatic runoff. The finalist who was preferred by (scored higher by) more voters wins the first seat. The next two highest scoring candidates then runoff, with the finalist preferred by more voters winning the next seat. This process continues until all positions are filled.
  • Cumulative voting: In this system, a voter facing multiple choices is given X number of points. The voter can then assign his points to one or more of the choices, thus enabling one to weight one's vote if desired. This could be achieved through a normalized ratings ballot, or through multiple plurality ballots, one per each point allocated. Typically, each voter will have as many votes as there are winners to be selected.
  • Single non-transferable vote: Each voter casts one vote for one candidate in a multi-candidate race for multiple offices
  • Bloc Plurality Voting: Each voter chooses as many candidates as there are seats to be elected. Add all the votes. Elect the candidates with the most votes until all positions are filled.

Sequential Proportional Methods[edit | edit source]

Sequential Cardinal Methods elect winners one at a time in sequence using a candidate selection method and a reweighting mechanism. The single-winner version of the selection is applied to find the first winner, then a reweighting is applied before the selection of the next and subsequent winners. A reweighting is applied to either the ballot or the scores for the ballot itself. The purpose of the reweighting phase is to ensure outcomes have a high level of Proportional representation by requiring them to satisfy criteria like the Hare Quota Criterion.

Common examples:

Optimal Proportional Methods[edit | edit source]

Optimal Systems select all winners at once by optimizing a specific desirable metric for proportionality. First a "quality function" or desired outcome is determined, and then an algorithm is used to determine the winner set that best maximizes that outcome. In most systems this is done by permuting to all possible winner sets not a maximization algorithm. This makes such systems computationally expensive. Since ranks do not allow for the arithmatic operations to do such calculations. As such there are no optimal Ordinal voting systems but only optimal Cardinal voting systems

Common examples:

Local district clusters vs Multi-member districts[edit | edit source]

There is an alternative to running a Multi-winner system in a Multi-member district. This is the concept of local district clusters. The traditional Multi-member districts just take the single member districts and combine them while this method would just link them into a cluster. Lets take 5 for example. All single member districts are combined into clusters of 5 with 5 seats up for grabs and most major parties running 5 candidates. What the difference is in this “Local” system is that each candidate would be elected to a specific single member district inside the cluster of 5. So the first winner would eliminate all other candidates running in the district they won. This of course means that all multi-member systems can be adapted to run in local clusters. The purported inventor of this alternative is Byron Becker for his Local PR system.

Pros[edit | edit source]

  • Improved Proportionate representation: Each elected representative is responsible for a smaller area and can focus on the specific issues important to the citizens of that region .
  • Improved Petitioner Accountability: Each citizen from that district has a specific representative for local issues who can be held to account. ie issues with traffic/schools/hospitals can't have the buck passed by blaming other representative. For partisan issues they would go to the representative in their cluster who is most likely to agree with them like in STV.

Cons[edit | edit source]

All the "best" candidates may be running in one district so when it is won they don't compete in other races. The parties would have to decide who to run in what riding. It has been argues that a system where representative have to at least have a mailing address in the riding they hope to represent is important for representation. In the last 2015 Canadian federal election an MP won a district without having a mailing address in Canada.