Wikipedia

STAR voting

(Redirected from Score Runoff Voting)

STAR voting is an electoral system for single-seat elections.[1][2] 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 finalists with the highest total scores, followed by an "automatic runoff" in which the finalist who is preferred on more ballots wins. It is a type of cardinal voting electoral system.

Image shows a ballot that allows voters to score candidates from 0 up to 5 stars. From the top down, the ballot contains the STAR Voting logo, then ballot instructions, then the candidates along with scores filled in for each, and lastly an explanation of how STAR Voting is counted.
The STAR voting ballot, including recommended instructions and formatting details
Graphic explaining how STAR Voting works

Method

edit

In STAR, voters are given a score ballot (or ratings ballot) on which each voter scores candidates with a number from 0 up to 5, with 0 representing "worst" and 5 representing "best". The scores for each candidate are then summed, and the two highest-scored candidates are selected as finalists. In the automatic runoff round, the finalist who was given a higher score on a greater number of ballots is selected as the winner.

Usage

edit

The concept was first proposed in October 2014 by Mark Frohnmayer, and was initially called score runoff voting (SRV).[3] The runoff step was introduced in order to reduce strategic incentives in ordinary score voting, such as bullet voting and tactical maximization.[4] STAR is intended to be a hybrid between (rated) score voting and (ranked) instant runoff voting.[5][6]

The first movement to implement STAR voting was centered in Oregon,[7][8] with chapters in Eugene, Portland, Salem, Astoria, and Ashland.[9] In July 2018, supporters submitted over 16,000 signatures for a ballot initiative in Lane County, Oregon, putting Measure 20-290 on the November 2018 ballot.[1][10][11][12] This ballot measure did not pass, with 47.6% of voters voting yes, and 52.4% of voters voting no.[13][14]

In 2019, the Multnomah County Democratic Party adopted STAR for all internal elections.[15][16] A 2020 ballot initiative for the city of Eugene (in which a 54% majority had supported the 2018 county initiative) was attempted, as well as a second attempt at Lane County,[17] and an initiative in Troutdale, Oregon.[18] On July 27, 2020, after the Eugene City Council deadlocked at 4-4 on a vote to refer a measure allowing STAR voting to be used in city elections to the November 2020 ballot, Eugene Mayor Lucy Vinis cast the deciding vote against the referral, meaning that no Eugene ballot measure would be held in 2020.[19]

The Independent Party of Oregon used STAR voting in their 2020 primary election.[20][21][22][23] The Democratic Party of Oregon used STAR Voting for their elections for delegates to the 2020 Democratic convention.[23] In 2022, the Libertarian Party of Oregon authorized STAR voting for its internal elections starting in 2023.[24] In 2024, the city council of Oakridge, Oregon, voted 5-1 to place a STAR voting measure on the November ballot. The measure would have implemented STAR voting for the following three elections before holding a vote on whether to permanently adopt it.[25] However, the measure failed with 46% approval.[26]

Example

edit

 

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
  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 score from 0 to 5 stars 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, 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 second-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.

Ties

edit

Although tie votes in STAR Voting are rare, 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 cannot be broken as above are considered a true tie.[27]

Properties

edit

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.[28][29] It also satisfies the resolvability criterion (in both Tideman and Woodall's versions).[citation needed]

There are a number of other voting system criteria it does not satisfy. These include the majority criterion, as it can happen that a candidate does not make it to the runoff, even though he is the first preference of a majority.[30] 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 three candidates). It also violates participation, consistency; and independence of clones (where any clones of the highest rated candidate may receive almost the same rating and enter the runoff, ahead of the second most popular non-clone). 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.[31]

See also

edit

Notes

edit
  1. ^ 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.
  2. ^ "Equal Vote Coalition". Retrieved 2017-04-05.
  3. ^ "Score Runoff Voting: The New Voting Method that Could Save Our Democratic Process". Independent Voter Network. 2016-12-08. Retrieved 2017-04-05.
  4. ^ "Strategic SRV?". Equal Vote Coalition. Retrieved 2017-04-05.
  5. ^ "Equal Systems Science". Equal Vote Coalition. Retrieved 2018-07-14. a two-phase, one-election hybrid of the Rating and Ranked Choice categories
  6. ^ "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
  7. ^ Russo, Ed. "New way to elect Lane County leaders could appear on ballot". The Register-Guard.
  8. ^ "Residents could put STAR Voting on November ballot".
  9. ^ "Chapters". STAR Voting. Retrieved 2020-01-09.
  10. ^ "STAR Voting on Nov ballot!". STAR Voting For Lane County. Retrieved 2018-09-19.
  11. ^ "November 6, 2018 General Election - Lane County". www.lanecounty.org. Retrieved 2018-09-19.
  12. ^ "Content Manager WebDrawer - 2018 General Election Voters Pamphlet Book 4 Lane County". records.sos.state.or.us.
  13. ^ Foden-Vencil, Kristian (November 7, 2018). "Lane County, Oregon, Effort To Change Voting System Fails". Oregon Public Broadcasting. Retrieved 2018-11-10.
  14. ^ "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
  15. ^ Barker, Joel (2019-10-01). "Multnomah County Democrats Adopt STAR voting for internal party elections". Multnomah County Democrats. Retrieved 2020-01-09.
  16. ^ Davis, James (16 March 2021). "STAR Voting Helps Create Smooth Party Elections". Multnomah County Democrats.
  17. ^ Hill, Christian. "STAR voting returns with dual initiative push". The Register-Guard. Archived from the original on 2020-09-25. Retrieved 2020-01-09.
  18. ^ "Campaigns". STAR Voting.
  19. ^ "Death STAR". July 29, 2020. Retrieved August 1, 2020.
  20. ^ "Independent Party of OR to use STAR Voting for Primary Election!". STAR Voting Email Campaign Archive. April 7, 2020. Retrieved 2020-04-08.
  21. ^ "STAR VOTING ANNOUNCEMENT". Independent Party of Oregon. Salem. 2020-04-07. Retrieved 2020-04-11.
  22. ^ "Independent Party of Oregon to utilize STAR system for primary". Herald and News. Apr 8, 2020. Retrieved 2020-04-10.
  23. ^ a b "Case Studies". STAR Voting.
  24. ^ "Libertarian Party of Oregon: 2022 Primary Elections Results". 11 March 2022.
  25. ^ "Oakridge voters to decide on 'STAR Voting' this November". KLCC | NPR for Oregonians. 2024-09-10. Retrieved 2024-10-02.
  26. ^ "City council ballot measures election results". 2024-11-09.
  27. ^ "Q: How are ties in STAR Voting broken?". STAR Voting. Retrieved October 21, 2024.
  28. ^ "An analysis of FairVote's Look at STAR Voting". Equal Vote Coalition. Retrieved 2018-07-21. STAR is monotonic, IRV is not.
  29. ^ 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.
  30. ^ League of Women Voters of Washington Education Fund. A Review of Various Election Methods (PDF) (Updated February 2020 ed.).
  31. ^ "Farewell to Pass/Fail". STAR Voting. Archived from the original on 2018-07-21. 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
edit
Retrieved from "https://en.wikipedia.org/w/index.php?title=STAR_voting&oldid=1256440228"