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STAR voting

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.

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.

Contents

UsageEdit

Political useEdit

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]

TypesEdit

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.

ExampleEdit

 

Imagine that Tennessee is having an election on the location of its capital. The population of Tennessee is concentrated around its four major cities, which are spread throughout the state. For this example, suppose that the entire electorate lives in these four cities and that everyone wants to live as near to the capital as possible.

The candidates for the capital are:

  • Memphis, the state's largest city, with 42% of the voters, but located far from the other cities
  • Nashville, with 26% of the voters, near the center of the state
  • Knoxville, with 17% of the voters
  • Chattanooga, with 15% of the voters

The preferences of the voters would be divided like this:

42% of voters
(close to Memphis)
26% of voters
(close to Nashville)
15% of voters
(close to Chattanooga)
17% of voters
(close to Knoxville)
  1. Memphis
  2. Nashville
  3. Chattanooga
  4. Knoxville
  1. Nashville
  2. Chattanooga
  3. Knoxville
  4. Memphis
  1. Chattanooga
  2. Knoxville
  3. Nashville
  4. Memphis
  1. Knoxville
  2. Chattanooga
  3. Nashville
  4. Memphis

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.

PropertiesEdit

Unlike ranked voting systems, STAR voting allows voters to express preferences of varying strengths.

STAR voting satisfies the monotonicity criterion in the sense that is usually used for cardinal voting methods, 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] STAR voting violates the monotonicity criterion in the sense that is usually used for ranked voting methods.[11] That is to say, if a voter raises the rating of a candidate and also lowers the rating of some other candidate, it may lower the chance of winning of both. For example: The main consequence of the fact that traditional runoff methods violate the monotonicity criterion is that it is a useful strategy for a voter to give an insincerely good ranking to a candidate who can be beaten by this voter's favorite candidate in the runoff. Also in STAR voting, it is a useful strategy for a voter to give an insincerely good rating to a candidate who can be beaten by this voter's favorite candidate in the runoff.

It also satisfies the resolvability criterion.[clarification needed][citation needed] It does not satisfy the majority criterion, since the majority winner may not get into the runoff. It does not satisfy the mutual majority criterion, although if there is a majority that gives some set of 2 or more candidates the highest rating and no more than 1 other candidate a rating above zero, then one of the mutual majority candidates must win. It does not satisfy reversal symmetry, independence of clones, participation, nor consistency. It also 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] and it does satisfy the Condorcet loser criterion. 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.[13] 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 alsoEdit

NotesEdit

  1. ^ "STAR voting - front page". starvoting.us. Retrieved 2018-07-10. 
  2. ^ 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. 
  3. ^ "Equal Vote Coalition". Retrieved 2017-04-05. 
  4. ^ Shentrup, Clay (2018-08-04). "The birth of STAR Voting". Twitter. Retrieved 2018-08-06. 
  5. ^ "Score Runoff Voting: The New Voting Method that Could Save Our Democratic Process". Independent Voter Network. 2016-12-08. Retrieved 2017-04-05. 
  6. ^ "Strategic SRV?". Equal Vote Coalition. Retrieved 2017-04-05. 
  7. ^ "Equal Systems Science". Equal Vote Coalition. Retrieved 2018-07-14. a two-phase, one-election hybrid of the Rating and Ranked Choice categories 
  8. ^ "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 
  9. ^ "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 
  10. ^ "An analysis of FairVote's Look at STAR Voting". Equal Vote Coalition. Retrieved 2018-07-21. STAR is monotonic, IRV is not. 
  11. ^ "STAR voting". The Center for Range Voting. Retrieved 2018-08-03. STAR elections can be nonmonotonic with a slightly wider sense of the word. 
  12. ^ Laslier, J.-F. (2006) "Strategic approval voting in a large electorate," IDEP Working Papers No. 405 (Marseille, France: Institut D'Economie Publique)
  13. ^ "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 linksEdit