STAR voting: Difference between revisions
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(Removed unofficial variations and added the official variations of STAR Voting for multi-winner elections, with citations. The methods previously described under this section are not STAR Voting and should be described on their own pages and with their own names if they are important to the previous authors. I also made some edits throughout to correct inaccuracies, add details, and add citations. While Score voting is a family of methods in which xyz, STAR is a specific method being advocated.) |
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{{wikipedia}}'''STAR voting'''<ref>{{Cite web |url = https://www.starvoting.us/ |title = STAR voting - front page |last = |first = |date = |website = starvoting.us |publisher = |access-date = 2018-07-10 |quote = STAR voting. |archive-url=|archive-date=|url-status=live}}</ref><ref>{{Cite news |url = https://ivn.us/2018/07/09/revolutionary-new-voting-method-bolstered-16000-voters-oregon-county/ |title = Revolutionary New Voting Method Bolstered By over 16,000 Voters in Oregon County |date = 2015-07-09 |newspaper = The Independent Voter Network |access-date = 2016-07-10 |last=|first=|url-status=live}}</ref> is an [[Voting method|electoral system]] [[:Category:Single-winner voting methods|for single-seat elections]]. The name stands for "score then automatic runoff", referring to the fact that this system is a combination of [[score voting]] and [[runoff voting]]. It is a type of [[cardinal voting]] electoral system. It was previously known as '''score runoff voting''' ('''SRV'''). |
{{wikipedia}}'''STAR voting'''<ref>{{Cite web |url = https://www.starvoting.us/ |title = STAR voting - front page |last = |first = |date = |website = starvoting.us |publisher = |access-date = 2018-07-10 |quote = STAR voting. |archive-url=|archive-date=|url-status=live}}</ref><ref>{{Cite news |url = https://ivn.us/2018/07/09/revolutionary-new-voting-method-bolstered-16000-voters-oregon-county/ |title = Revolutionary New Voting Method Bolstered By over 16,000 Voters in Oregon County |date = 2015-07-09 |newspaper = The Independent Voter Network |access-date = 2016-07-10 |last=|first=|url-status=live}}</ref> is an [[Voting method|electoral system]] [[:Category:Single-winner voting methods|for single-seat elections]], though variations exist for multi-seat and multi-seat proportional representation elections. The name stands for "score then automatic runoff", referring to the fact that this system is a combination of [[score voting]] and [[runoff voting]]. It is a type of [[cardinal voting]] electoral system. It was previously known as '''score runoff voting''' ('''SRV'''). |
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[[File:Score Runoff Voting sample presidential ballot.png|thumb|STAR voting uses a standard Score Voting ballot. The counting method adds an extra step to yield the preference winner between the top two scoring candidates overall.]] |
[[File:Score Runoff Voting sample presidential ballot.png|thumb|STAR voting uses a standard Score Voting ballot. The counting method adds an extra step to yield the preference winner between the top two scoring candidates overall.]] |
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Voters cast ballots as in score voting, rating each candidate |
Voters cast ballots as in score voting, rating each candidate from 0-5. The two candidates with the highest total are selected as finalists, and then in the "automatic runoff", the finalist who is preferred on more ballots wins. |
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== Usage == |
== Usage == |
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The concept was first proposed publicly in October 2014 by Center for Election Science co-founder Clay Shentrup.<ref>{{Cite web |url = https://groups.google.com/d/msg/electionscience/JK82EFn7nrs/Lble3V2CW4UJ |title = Google Groups |website = groups.google.com |access-date = 2017-04-05 }}</ref> The runoff step was introduced in order to correct for strategic distortion in ordinary score voting,<ref>{{Cite web |url = https://ivn.us/2016/12/08/score-runoff-voting/ |title = Score Runoff Voting: The New Voting Method that Could Save Our Democratic Process |date = 2016-12-08 |website = IVN.us |access-date = 2017-04-05 }}</ref> such as [[bullet voting]] and tactical maximization.<ref>{{Cite news |url = http://equal.vote/strategic_srv |title = Strategic SRV? - Equal Vote Coalition |work = Equal Vote Coalition |access-date = 2017-04-05 }}</ref> Thus, STAR is intended to be a compromise between [[score voting]] and [[instant runoff voting]].<ref>{{Cite news |url = http://equal.vote |title = Equal Vote Coalition |work = Equal Vote Coalition |access-date = 2017-04-05 }}</ref> The movement to implement STAR voting was centered in [[w:Oregon|Oregon]], and in July 2018, supporters submitted over 16,000 signatures for a ballot initiative in [[w:Lane County, OR|Lane County]]. |
The concept was invented by Mark Frohnmayer and Clay Shentrup<ref>{{Cite web|url=http://starvoting.us/about|title=|last=|first=|date=|website=|url-status=live|archive-url=|archive-date=|access-date=}}</ref> and was first proposed publicly in October 2014 by Center for Election Science co-founder Clay Shentrup.<ref>{{Cite web |url = https://groups.google.com/d/msg/electionscience/JK82EFn7nrs/Lble3V2CW4UJ |title = Google Groups |website = groups.google.com |access-date = 2017-04-05 }}</ref> The runoff step was introduced in order to correct for strategic distortion in ordinary score voting,<ref>{{Cite web |url = https://ivn.us/2016/12/08/score-runoff-voting/ |title = Score Runoff Voting: The New Voting Method that Could Save Our Democratic Process |date = 2016-12-08 |website = IVN.us |access-date = 2017-04-05 }}</ref> such as [[bullet voting]] and tactical maximization.<ref>{{Cite news |url = http://equal.vote/strategic_srv |title = Strategic SRV? - Equal Vote Coalition |work = Equal Vote Coalition |access-date = 2017-04-05 }}</ref> Thus, STAR is intended to be a compromise between [[score voting]] and [[instant runoff voting]].<ref>{{Cite news |url = http://equal.vote |title = Equal Vote Coalition |work = Equal Vote Coalition |access-date = 2017-04-05 }}</ref> The movement to implement STAR voting was initially centered in [[w:Oregon|Oregon]], and in July 2018, supporters submitted over 16,000 signatures for a ballot initiative in [[w:Lane County, OR|Lane County]]. The initiative received 47.6% of the vote. Ballot initiatives are currently underway for Lane County, Eugene, and Troutdale, Oregon. <ref>{{Cite web|url=http://starvoting.us/campaigns|title=STAR Voting Campaigns|last=|first=|date=|website=STAR Voting|url-status=live|archive-url=|archive-date=|access-date=}}</ref> |
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==Method== |
==Method== |
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STAR voting uses a [[ratings ballot]]; |
STAR voting uses a [[ratings ballot]]; each voter scores each candidate from 0 to 5 stars.<ref>{{Cite web |url = http://rangevoting.org/RateScaleResearch.html |title = Rating Scale Research |last = |first = |date = |website = RangeVoting.org |publisher = |access-date = 2016-12-11 |quote = The evidence surveyed here currently suggests that the "best" scale for human voters should have 10 levels }}</ref> Candidates who are left blank receive a 0. No preference can be indicated by giving multiple candidates the same score. The scores for each candidate are then summed, and the two candidates with the highest sums go to the runoff. Of these two, the one that is scored higher on a greater number of ballots is the winner. |
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==Ties== |
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Tie votes in STAR Voting are rare, but as with any voting method they can occur, especially in elections without many voters. In most cases, ties in STAR voting can be broken by referring back to the ballots themselves for either the Scoring or Runoff round. Ties in the Scoring round are broken in favor of the candidate who was preferred by more voters. Ties in the Runoff round are broken in favor of the candidate who was scored higher. Ties which can not be broken as above are considered a true tie. <ref>https://www.starvoting.us/ties</ref> |
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==Example== |
==Example== |
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{{Tenn voting example}} |
{{Tenn voting example}} |
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For comparison, note that traditional [[first-past-the-post]] would elect Memphis, even though most citizens consider it the worst choice, because 42% is larger than any other single city. [[Instant-runoff voting#Tennessee capital election|Instant-runoff voting]] would elect the 2nd-worst choice (Knoxville), because the central candidates would be eliminated early. In [[Approval voting]], with each voter selecting their top two cities, Nashville would win because of the significant boost from Memphis residents. A [[Two-round system#Example II|two-round system]] would have a runoff between Memphis and Nashville where Nashville would win. |
For comparison, note that traditional [[first-past-the-post]] would elect Memphis, even though most citizens consider it the worst choice, because 42% is larger than any other single city. [[Instant-runoff voting#Tennessee capital election|Instant-runoff voting]] would elect the 2nd-worst choice (Knoxville), because the central candidates would be eliminated early. In [[Approval voting]], with each voter selecting their top two cities, Nashville would win because of the significant boost from Memphis residents. A [[Two-round system#Example II|two-round system]] would have a runoff between Memphis and Nashville where Nashville would win. |
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==Variations== |
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STAR Voting can be used for multi-winner elections as in STAR bloc voting or it can be used for proportional representation elections. |
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'''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. <ref>{{Cite web|url=https://electowiki.org/wiki/Bloc_voting|title=Bloc voting|last=|first=|date=|website=|url-status=live|archive-url=|archive-date=|access-date=}}</ref> |
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'''Proportional STAR Voting:''' Each voter scores all the candidates on a scale from 0-5. The results are tabulated using a proportional STAR algorithm such as Sequentially Spent STAR. <ref>{{Cite web|url=https://electowiki.org/wiki/Sequentially_Spent_Score|title=Sequentially Spent Score|last=|first=|date=|website=|url-status=live|archive-url=|archive-date=|access-date=}}</ref> The Equal Vote Coalition is in the process of determining the official recommendation for proportional STAR Voting (STAR-PR.) <ref>{{Cite web|url=http://starvoting.us/star_pr|title=0-5 Star Proportional Research Committee|last=|first=|date=|website=|url-status=live|archive-url=|archive-date=|access-date=}}</ref> |
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==Properties== |
==Properties== |
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STAR voting allows voters to express |
STAR voting allows voters to express both preference order and degree of support. |
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STAR voting satisfies the [[monotonicity criterion]], i.e. raising your vote's score for a candidate can never hurt their chances of winning, and lowering it can never help their chances. It fails several generalized versions of monotonicity that [[Score voting]] passes. |
STAR voting satisfies the [[monotonicity criterion]], i.e. raising your vote's score for a candidate can never hurt their chances of winning, and lowering it can never help their chances. It fails several generalized versions of monotonicity that [[Score voting]] passes. |
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For simplicity, the candidates have been sorted by scores, with their scores in bold in their own pairwise comparison cell. The top two candidates are not tied scorewise with anyone else, so they both are in the automatic runoff. Between the two, "I don't like party politics" is pairwise preferred (has 4 more votes in the matchup), so it wins. |
For simplicity, the candidates have been sorted by scores, with their scores in bold in their own pairwise comparison cell. The top two candidates are not tied scorewise with anyone else, so they both are in the automatic runoff. Between the two, "I don't like party politics" is pairwise preferred (has 4 more votes in the matchup), so it wins. |
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== Modifications == |
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A modification to STAR that takes degree of preference more into account would be to make each voter's vote in the runoff only as strong as the highest score they gave to any candidate. In other words, a voter who gave their favorite a 3/5 (3 out of 5) would have only 3/5ths of a vote in the runoff, rather than a full vote. This modification allows voters to express less-than-full support for any candidate in both the score round and the runoff. |
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Example: <blockquote>2 A:1 D:5 |
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3 A:5 |
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6 B:4 |
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Scores are A 17 B 24 D 10, with B pairwise beating A 6 to 5. So the Score and STAR winner is B. But taking into account that those who preferred B over A all have their favorite a maximum of a 4 out of 5, if we weight their runoff votes at 80%, then now B loses the runoff 4.8 to 5. So A wins under modified STAR.<ref>https://forum.electionscience.org/t/star-but-with-weak-votes-in-the-runoff-when-voters-dont-give-any-candidate-the-top-score/615/5</ref></blockquote>Voters could also be allowed to indicate they want their rated preference to be used in the runoff, rather than ranked preferences i.e. a voter who scored the two candidates a 5/5 and 3/5 would give 1 vote to the first candidate and 0.6 votes to the second. This is related to [[Rated pairwise preference ballot#Rated or ranked preference]], and the vote-counting can be done in the same way. |
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[[Instant Runoff Normalized Ratings|IRNR]] is related to STAR in the same way that [[IRV]] is related to [[Top-two runoff]]. |
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Given that STAR is an automatic form of Score voting + Runoff, one can also create an automatic "[[Approval voting]] + Runoff" method by allowing voters to rank or score candidates, and then indicate an [[Condorcet//Approval|approval threshold]] for a particular rank or score such that they'd approve all candidates at that same rank or score or a higher rank or score, and then use the ranks or scores to figure out which of the two most approved candidates is preferred by a majority. |
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== Notes == |
== Notes == |
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