|
== RCIPE STV ==
The RCIPE method can be extended to elect multiple candidates, such as when electing non-partisan members of a city council, or when electing two (or more) representatives from the same district. This means the RCIPE STV method can be used as a direct replacement for the [[Single transferable vote|Single Transferable Vote]] (STV).
The RCIPE STV method modifiesuses the [[Singlefollowing transferablerules vote|Singleto Transferableelect Vote]]two (STV)or methodmore incandidates theto followingfill two or more equivalent waysseats:
* At the beginning of all the counting rounds, each ballot has an influence amount equal to one vote. During a counting round that elects a candidate, some ballots are given zero influence for future counting rounds. This reduced influence increases the influence of the other ballots to compensate for their lack of support for already-elected candidates. The result is that the elected candidates represent most of the voters, not just a majority of voters.
* During each round of counting either one candidate is elected, or one candidate is eliminated, but not both in the same round.
* At the beginning of each counting round, theeach transfercandidate countgets fora eachtransfer candidate is resetcount toof zero.
* AtDuring the beginning of all thea counting roundsround, each ballot that has anfull influence amount equal toadds one vote. Duringcount laterto countingthe roundstransfer acount ballotof canthe havecandidate awho reducedis influenceranked higher amounton that isballot expressedthan asany aother decimalcandidate numberwho thathas cannot rangeyet frombeen zeroelected upor to oneeliminated. If a law makes it illegal for a ballot tohas have anzero influence, amountit otherdoes thannot zero or one,change the countingtransfer processcount can be modified asof describedany belowcandidate.
* At the end of a counting round, the candidate with the highest transfer count is elected if that candidate's transfer count equals or exceeds the required quota count . The quota count is different for each counting round. Any reasonable formula for quota counts can be used. ▼* When counting a ballot, the ballot's influence amount is added to the transfer count of the candidate who is ranked highest after ignoring the marks for already-elected and already-eliminated candidates.
* The quota count can change after each candidate is elected. Any reasonable formula for quota counts can be used.
* If a ballot ranks two or more candidates at the same preference level, and if there are not any remaining (not-yet-elected and not-yet-eliminated) candidates ranked higher on this ballot, then this ballot's influence amount is equally split among the remaining candidates who are ranked at that shared preference level. For example, if a ballot ranks candidate A highest, and ranks candidates B, C, and D at the next-highest level, and if candidates A and B have been elected or eliminated, then half of this ballot's influence amount transfers to candidate C and the other half transfers to candidate D. ▼* IfAt the end of a counting round, if all the candidates have transfer counts that are less than the current quota numbercount, and if there is a pairwise losing candidate during that round, the pairwise losing candidate is eliminated . A pairwise losing candidate is a candidate who would lose every one-on-one match against every other remaining (not-yet-elected and not-yet-eliminated) candidate. During pairwise counting all the ballots are counted, but somethe ballots canthat have reducedzero influence do not contribute any votes to either side of the one-on-one matches. ▼▲* At the end of a counting round, the candidate with the highest transfer count is elected if that candidate's transfer count equals or exceeds the required quota count. The quota count is different for each counting round. Any reasonable formula for quota counts can be used.
▲* If all the candidates have transfer counts that are less than the quota number, and if there is a pairwise losing candidate during that round, the pairwise losing candidate is eliminated. During pairwise counting all the ballots are counted, but some ballots can have reduced influence.
* If a counting round does not elect a candidate and there is no pairwise losing candidate, then the candidate with the lowest transfer count is eliminated.
* When a counting round ends with a candidate isgetting elected, all the ballots that contribute full (not-reduced) influencecontributed to the candidate's transfer count haveof theirthat influenceelected reducedcandidate toare identified as the candidate'ssupporting excessballots, transferand a quota count dividednumber byof thethese transfersupporting count,ballots are given zero influence for all future counting rounds. whereAll the excesssupporting transferballots countdo equalsnot get zero influence because the candidate'snumber transferof countsupporting minusballots beyond the quota count. Ofis coursean decimalexcess calculationlevel resultsof aresupport roundedthat down,must notbe upallowed to contribute toward electing another candidate.
* The specific supporting ballots that are changed from full influence to zero influence are chosen to be equally spaced from one another in the supplied ballot sequence, without including the already-zero-influence ballots in the equal-spacing calculations. The goal of this selection process, or any alternate selection process, is to ensure that a different supplied ballot sequence cannot change the results.
* When a candidate is elected, all the ballots that contribute reduced influence (less than full influence) to that candidate's transfer count are reduced to have zero influence in future counting rounds.
▲* If a full-influence ballot ranks two or more remaining (not-yet-elected and not-yet-eliminated) candidates at the same preference level, and if there are not any remaining (not-yet-elected and not-yet-eliminated) candidates ranked higher on this ballot, then this ballot 's is grouped with other similar, although not necessarily identical, ballots and their influence amountcounts isare equally split among the remaining candidates who are ranked at that shared preference level. For example, if candidates A and B have been elected or eliminated, and a ballot ranks candidate A highest , and ranks candidates B, C, and D at the next-highest level, and ifanother ballot ranks candidate B highest and ranks candidates A , C, and BD haveat beenthe electednext-highest or eliminatedlevel, then halfone of thisthese ballot's influencetwo amountballots transfers to candidate C and the other halfballot transfers to candidate D . The choice of which ballot transfers to which candidate must be handled so that supplying the same ballots in a different sequence is extremely likely to elect the same candidates.
If decimal influence amounts are not allowed, the following modifications can be used:
* Instead of giving a single reduced influence amount to ballots that support an elected candidate, some of the supporting ballots are given full influence and others are given zero influence.
* Selecting which ballots get full influence and which ballots get zero influence should make use of information about how many ballots share the same marking pattern. For example, if 100 ballots have the same marking pattern and the decimal calculation method would reduce their influence to 0.8 of a vote each, then selecting any 80 of these ballots to get full influence and giving the remaining 20 ballots zero influence produces the same result as the decimal approach.
* Ballots that have unique or uncommon marking patterns must be selected semi-randomly, yet the total number of supporting ballots getting zero influence must equal the quota count, and the total number of ballots getting full influence must equal the elected-candidate's transfer count minus the quota count.
* Instead of using the same semi-random selections from one counting round to the next, the semi-random selection process should be done for each counting round. This approach makes it unlikely that a specific ballot will get zero influence significantly more often than any other specific ballot that has similar markings.
* Ballots on which two or more remaining candidates share the same highest ranking level are distributed almost the same as in the decimal calculation method. The significant difference is that ballots with zero influence (during that counting round) are not distributed among the shared-level candidates.
Some jurisdictions may have laws that allow a ballot to have decimal influence amounts that range from zero to one. If this is allowed, the above rules can be modified to use decimal influence amounts.
[[Category:Sequential loser-elimination methods]]
[[Category:Ranked voting methods]]
| 