STAR voting
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STAR voting is an electoral system for single-seat elections.[1][2][3] The name (an allusion to star ratings) stands for "Score then Automatic Runoff", referring to the fact that this system is a combination of score voting, to pick two frontrunners with the highest total scores, followed by a "virtual runoff" in which the frontrunner who is preferred on more ballots wins. It is a type of cardinal voting electoral system.
Method
In STAR, voters are given a ratings ballot, on which each voter rates every candidate with a number from 0 to 5, where 0 means "strong disapproval" and 5 means "strong approval".
The scores for each candidate are then summed, and the two highest-rated candidates are selected as finalists.
In the instant-runoff round, the finalist who was given a higher rating on a greater number of ballots is selected as the winner.
Usage
The concept was first proposed in October 2014 by Mark Frohnmayer, and was initially called score plus top two or score runoff voting (SRV).[4] The runoff step was introduced in order to reduce strategic incentives in ordinary score voting, such as bullet voting and tactical maximization.[5] Thus, STAR is intended to be a hybrid between (rated) score voting and (ranked) instant runoff voting.[6][7] The movement to implement STAR voting was centered in Oregon[8][9], and in July 2018, supporters submitted over 16000 signatures for a ballot initiative in Lane County, OR, putting Measure 20-290 on the November 2018 ballot.[2][10][11][12] This ballot measured failed, with 47.6% of voters voting yes, and 52.4% of voters voting no.[13][14]
Example
Suppose that Tennessee is holding an election on the location of its capital. The population is concentrated around four major cities. All voters want the capital to be as close to them as possible. The options are:
- Memphis, the largest city, but far from the others (42% of voters)
- Nashville, near the center of the state (26% of voters)
- Chattanooga, somewhat east (15% of voters)
- Knoxville, far to the northeast (17% of voters)
The preferences of each region's voters are:
| 42% of voters Far-West |
26% of voters Center |
15% of voters Center-East |
17% of voters Far-East |
|---|---|---|---|
|
|
|
|
Suppose that 100 voters each decided to grant from 0 to 5 stars to each city such that their most liked choice got 5 stars, and least liked choice got 0 stars, with the intermediate choices getting an amount proportional to their relative distance.
| Voter from/ City Choice |
Memphis | Nashville | Chattanooga | Knoxville | Total |
|---|---|---|---|---|---|
| Memphis | 210 (42 × 5) | 0 (26 × 0) | 0 (15 × 0) | 0 (17 × 0) | 210 |
| Nashville | 84 (42 × 2) | 130 (26 × 5) | 45 (15 × 3) | 34 (17 × 2) | 293 |
| Chattanooga | 42 (42 × 1) | 52 (26 × 2) | 75 (15 × 5) | 68 (17 × 4) | 237 |
| Knoxville | 0 (42 × 0) | 26 (26 × 1) | 45 (15 × 3) | 85 (17 × 5) | 156 |
The top-two frontrunners are Nashville and Chattanooga. Of the two, Nashville is preferred by 68% (42+26) to 32% (15+17) of voters, so Nashville, the capital in real life, likewise wins in the example.
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 would elect the 2nd-worst choice (Knoxville), because the central candidates would be eliminated early. Under Score voting, Nashville would have won, since it had the highest score in the first round. In approval voting, with each voter selecting their top two cities, Nashville would also win because of the significant boost from Memphis residents. A two-round system would have a runoff between Memphis and Nashville, where Nashville would win.
In this particular case, there is no way for any single city of voters to get a better outcome through tactical voting. However, Chattanooga and Knoxville voters combined could vote strategically to make Chattanooga win; while Memphis and Nashville voters could defend against that strategy and ensure Nashville still won by strategically giving Nashville a higher rating and/or Chattanooga and Knoxville lower ratings.
Properties
Unlike ranked voting systems, STAR voting allows voters to express preferences of varying strengths.
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.[15][16] It also satisfies the resolvability criterion (in both Tideman and Woodall's versions).
It does not satisfy the Condorcet criterion (i.e., is not a Condorcet method), although with all-strategic voters and perfect information, the Condorcet winner is a strong Nash equilibrium.[17] It does, however, satisfy the Condorcet loser criterion and the majority loser criterion.[18]
There are a number of other voting system criteria it does not satisfy. These include the majority criterion, since the highest-rated candidates that proceed to the runoff may not be the first preference of a majority. It does not satisfy the mutual majority criterion, although the more candidates there are in the mutual majority set, the greater the chances that at least one of them is among the two finalists in the runoff, in which case one of them will win. It does not always satisfy reversal symmetry (though it only violates it for exactly 3 candidates). It also violates independence of clones, participation, and consistency. It does not satisfy the later-no-harm criterion, meaning that giving a positive rating to a less-preferred candidate can cause a more-preferred candidate to lose.[19]
Discussion of STAR's criteria compliances
STAR advocates claim that many of the criteria it fails are not paramount, as some are mutually exclusive, and no voting system can ever meet all such criteria simultaneously. For instance, they claim that STAR's failure on both Favorite Betrayal and Later No Harm is "only occasional"; better, they claim, than other systems which fail just one of those two incompatible criteria more consistently. As evidence, they point voter satisfaction simulations, on which STAR performs better than many other methods.[19]
FairVote, an organization that promotes the use of Ranked Choice Voting instead of STAR voting, disagrees. They argue that STAR's failure of the Majority criterion and the Later-No-Harm criterion is problematic.[20] Because of this, FairVote finds it difficult to assess other practical impacts of STAR voting and recommends greater experimentation in internal elections.[20]
See also
- List of democracy and elections-related topics
- Consensus decision-making
- Decision making
- Democracy
- Relative Utilitarianism
- Majority judgment — similar voting method, based on medians instead of averages
- Unified Primary — alternate voting method for nonpartisan blanket primary that uses approval voting-based method in runoff election
Notes
- ^ "STAR voting - front page". starvoting.us. Retrieved 2018-07-10.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ a b "Revolutionary New Voting Method Bolstered By over 16,000 Voters in Oregon County". The Independent Voter Network. 2018-07-09. Retrieved 2018-09-18.
- ^ "Equal Vote Coalition". Retrieved 2017-04-05.
- ^ "Score Runoff Voting: The New Voting Method that Could Save Our Democratic Process". Independent Voter Network. 2016-12-08. Retrieved 2017-04-05.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ "Strategic SRV?". Equal Vote Coalition. Retrieved 2017-04-05.
- ^ "Equal Systems Science". Equal Vote Coalition. Retrieved 2018-07-14.
a two-phase, one-election hybrid of the Rating and Ranked Choice categories
- ^ "Comparing Voting Systems: A Report Card". Equal Vote Coalition. Retrieved 2018-07-14.
STAR Voting is the new and improved hybrid of RCV and Score Voting
- ^ "Lane County could break ground on electing leaders".
- ^ "Residents could put STAR Voting on November ballot".
- ^ "STAR Voting on Nov ballot!". STAR Voting For Lane County. Retrieved 2018-09-19.
- ^ "November 6, 2018 General Election - Lane County". www.lanecounty.org. Retrieved 2018-09-19.
- ^ "Lane County Voters' Pamphlet, page 134: Measure 20-290" (PDF).
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ Foden-Vencil, Kristian (November 7, 2018). "Lane County, Oregon, Effort To Change Voting System Fails". Oregon Public Broadcasting. Retrieved 2018-11-10.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ "General Election Lane County, November 6, 2018 All Precincts, All Districts, All ScanStations, All Contests, All Boxes Unofficial Results" (PDF). November 7, 2018.
20-290 Lane County Adopts STAR Voting: Yes 74408, No 82157, Total 156565
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ "An analysis of FairVote's Look at STAR Voting". Equal Vote Coalition. Retrieved 2018-07-21.
STAR is monotonic, IRV is not.
- ^ D R Woodall, "Monotonicity and Single-Seat Election Rules", Voting matters, Issue 6, 1996. This article calls the monotonicity criterion in question "mono-raise", and also gives other monotonicity criteria that STAR voting fails. For instance, STAR voting violates "mono-raise-delete", defined as "A candidate X should not be harmed if X is raised on some ballots and all candidates now below X on those ballots are deleted from them". In the case of STAR, "deleted" would mean "given the lowest score"; deleting a candidate Y could change the runoff from X vs Y, which X wins, to X vs Z, which Z wins.
- ^ Laslier, J.-F. (2006) "Strategic approval voting in a large electorate," IDEP Working Papers No. 405 (Marseille, France: Institut D'Economie Publique)
- ^ Because of the limited number of scores available, when there are over 6 candidates voters who have a sincere preference are still forced to rate some candidates equal. Thus it is technically possible for a candidate to be a Condorcet and/or majority loser by sincere preferences, but not so going by ballots; and thus to win. However, this would not be true for a theoretical version of STAR where ratings are real numbers rather than whole numbers; and under any voter model where each voter is equally likely to express each successive preference, the probability of a Condorcet/majority loser winning under STAR approaches zero with even moderate numbers of voters.
- ^ a b "Farewell to Pass/Fail". STAR Voting. Retrieved 2018-07-21.
STAR Voting actually fails both Later No Harm and The Favorite Betrayal Criterion - but hear us out! This is actually also desirable. ... We believe it is better for a system to fail two opposing criteria and in doing so mitigate the ways in which it fails both
- ^ a b Richie, Rob (July 2018). "Explaining FairVote's position on STAR Voting". FairVote.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help)
External links
- STAR voting
- The Equal Vote Coalition, an advocacy organization for STAR voting and other reforms.
- ★.✓ An online platform for carrying out STAR voting elections.