STAR voting
An editor has nominated this article for deletion. You are welcome to participate in the deletion discussion, which will decide whether or not to retain it. |
| Part of the Politics series |
| Electoral systems |
|---|
.svg) |
 Politics portal |
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.
Usage
![[icon]](/wiki/File:Wiki_letter_w_cropped.svg){kind=small} | This section needs expansion. You can help by adding to it. (July 2018) |
Political use
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,[5] such as bullet voting and tactical maximization.[6] Thus, STAR is intended to be a hybrid between (rated) score voting and (ranked) instant runoff voting.[7][8] The movement to implement STAR voting was centered in Oregon, and in July 2018, supporters submitted over 16000 signatures for a ballot initiative in Lane County, OR. This is enough to qualify this proposal to be on the ballot, if the measure is deemed well-drafted.[2]
Types
STAR voting uses a ratings ballot; that is, each voter rates each candidate with a number within a specified range, such as 0 to 5 stars.[9] In the simplest system, all candidates must be rated. 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 higher on a greater number of ballots is the winner.
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 also 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 Chatanooga 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 Chatanooga 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.[10] [11] 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.[12] It does, however, satisfy the Condorcet loser criterion and the majority loser criterion.[13]
There are a number of other criteria it does not satisfy. These include the majority criterion, since the majority winner may not get into the runoff. 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.[14] It does not satisfy the later-no-help criterion, meaning that giving a positive rating to a less-preferred candidate can cause a more-preferred candidate to win.
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. 2015-07-09. Retrieved 2016-07-10.
- ^ "Equal Vote Coalition". Retrieved 2017-04-05.
- ^ Shentrup, Clay (2018-08-04). "The birth of STAR Voting". Twitter. Retrieved 2018-08-06.
{{cite web}}: Cite has empty unknown parameter:|dead-url=(help) - ^ "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
- ^ "Rating Scale Research". RangeVoting.org. Retrieved 2016-12-11.
The evidence surveyed here currently suggests that the "best" scale for human voters should have 10 levels
- ^ "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.
- ^ "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.
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.