STAR voting

Part of the Politics series
Electoral systems
Plurality/majoritarian Plurality First-past-the-post Single non-transferable vote Limited voting Plurality-at-large (block voting) General ticket Multi-round voting Two-round Exhaustive ballot Ranked/preferential systems Instant-runoff (alternative vote) Contingent vote Coombs' method Condorcet methods (Copeland's, Dodgson's, Kemeny-Young, Minimax, Nanson's, Ranked pairs, Schulze, Alternative Smith) Borda count Bucklin voting Oklahoma primary electoral system Preferential block voting Cardinal/graded systems Score voting Approval voting (Unified Primary) Multi-winner approval voting (Proportional, Sequential proportional, Satisfaction) Majority judgment STAR voting
Proportional representation Party-list (Open lists, Closed lists, Local lists) Highest averages (D'Hondt, Sainte-Laguë, Huntington-Hill) Largest remainder (Hare, Droop, Imperiali, Hagenbach-Bischoff) Single transferable vote (CPO-STV, Gregory, Schulze STV, Wright) Biproportional apportionment Fair majority voting
Mixed systems Mixed member proportional Additional Member System Parallel voting (Mixed member majoritarian) Scorporo Majority bonus Alternative Vote Plus Dual member proportional Rural-urban proportional
Other systems & related theory Cumulative voting Binomial voting Proxy voting Delegated voting Random selection (Sortition, Random ballot) Comparison of electoral systems Social choice theory Arrow's theorem Gibbard–Satterthwaite theorem Public choice theory
Politics portal

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.

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,^[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^[9][10], 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][11][12][13]}

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.^[14] 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 rated higher on a greater number of ballots is the winner.

Example

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:

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.

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 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] 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.

These criteria are not considered important by STAR advocates, as some are mutually exclusive, and no voting system can ever meet all such criteria simultaneously. Advocates claim that STAR strikes a balance between such competing criteria, and performs better than other systems in voter satisfaction simulations.^[19]

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

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.