Center squeeze: Difference between revisions
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The '''center squeeze effect''' refers to a class of voting scenarios
Note, however, that methods avoiding center squeeze can also incentivize strategy if one of the wings thinks they can squeeze out victory for their preferred candidate by concealing their support for the center. [[Bullet vote|Bullet voting]] in [[approval voting]] is an example of this; see [[Chicken dilemma]] for more information.
Voting systems that suffer from the center-squeeze effect exhibit a bias in favor of more extreme candidates, which leads to unrepresentative winners and political polarization.<ref name=":3">{{Cite book|url=https://link.springer.com/10.1007/978-3-642-02839-7|title=Handbook on Approval Voting|date=2010|publisher=Springer Berlin Heidelberg|isbn=978-3-642-02838-0|editor-last=Laslier|editor-first=Jean-François|series=Studies in Choice and Welfare|location=Berlin, Heidelberg|pages=2|language=en|doi=10.1007/978-3-642-02839-7|quote=By eliminating the squeezing effect, Approval Voting would encourage the election of consensual candidates. The squeezing effect is typically observed in multiparty elections with a runoff. The runoff tends to prevent extremist candidates from winning, but a centrist candidate who would win any pairwise runoff (the “Condorcet winner”) is also often “squeezed” between the left-wing and the right-wing candidates and so eliminated in the first round.|editor-last2=Sanver|editor-first2=M. Remzi}}</ref><ref name=":4">{{Cite web|url=https://thehill.com/opinion/campaign/3711206-the-flaw-in-ranked-choice-voting-rewarding-extremists/|title=The flaw in ranked-choice voting: rewarding extremists|last=Atkinson|first=Nathan|last2=Ganz|first2=Scott C.|date=2022-10-30|website=The Hill|language=en-US|access-date=2023-05-14|quote=However, ranked-choice voting makes it more difficult to elect moderate candidates when the electorate is polarized. For example, in a three-person race, the moderate candidate may be preferred to each of the more extreme candidates by a majority of voters. However, voters with far-left and far-right views will rank the candidate in second place rather than in first place. Since ranked-choice voting counts only the number of first-choice votes (among the remaining candidates), the moderate candidate would be eliminated in the first round, leaving one of the extreme candidates to be declared the winner.}}</ref>
(Note that "center" does not refer to an absolute political spectrum, but relative to the ideologies of the voters. If the Libertarian Party holds an election, for instance, the winner should be near the center of Libertarian ideology, but if there are other candidates to either side, the most-representative candidate cannot win. This also doesn't imply any particular spectrum, such as the American left-right political spectrum; it could be any attribute on which candidates are evaluated, or multiple such attributes.<ref name=":1">{{Cite journal|last1=Davis|first1=Otto A.|last2=Hinich|first2=Melvin J.|last3=Ordeshook|first3=Peter C.|date=1970-01-01|title=An Expository Development of a Mathematical Model of the Electoral Process|url=https://semanticscholar.org/paper/66661f9678dbe956e525e87a50b5b4ee6bf280f1|journal=The American Political Science Review|volume=64|issue=2|pages=426–448|doi=10.2307/1953842|jstor=1953842|quote=Since our model is multi-dimensional, we can incorporate all criteria which we normally associate with a citizen's voting decision process — issues, style, partisan identification, and the like.|s2cid=}}</ref>)
While typically illustrated in a simple case with three candidates, the effect can occur with any number of candidates: In systems that suffer from center squeeze, the more candidates there are crowding the center, the less likely a good representative is to win. It may eliminate not just the highest-ranked/rated candidate, but also the 2nd-highest, 3rd-highest, and so on.
== Three-candidate example ==
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{{ballots|
1031: A>B>C
415: B>A>C
446: B>C>A
1108: C>B>A
}}
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On a 2-dimensional political compass with 3 candidates, candidate B is the Condorcet winner and utilitarian winner, but is squeezed out by A and C on either side:
[[File:2D election example A vs B vs C.png]]
<!--{{Graph:Chart|width=200|height=150▼
|xAxisTitle=Candidates|yAxisTitle=Votes|type=rect
|x=A, B, C
|y=1031, 861, 1108
|colors=#1f77b4, #ff7f0e, #2ca02c
}}-->
[[File:Center Squeeze (before).svg|frameless]]
C would win under a single-round of FPTP, but if there is a runoff, then more of B's votes transfer to A, making A the winner:
[[File:2D election example A vs C.png]]
<!--{{Graph:Chart|width=200|height=150
▲{{Graph:Chart|width=200|height=150
|xAxisTitle=Candidates|yAxisTitle=Votes|type=rect
|x=A, B, C
|y=1619, 0, 1381
|colors=#1f77b4, #ff7f0e, #2ca02c
}}
[[File:Center Squeeze (after).svg|frameless]]
Either way, the winner is not as good of a representative of the electorate as candidate B.
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== Prevalence ==
Voting systems that have serious problems with center squeeze include [[First Past the Post electoral system|FPTP]],<ref name=":2" /> two-round [[runoff voting]],<ref name=":2" /> and [[IRV]].<ref name=":0" /><ref>{{Cite journal|last=Verma|first=Dhruv|date=2021-01-01|title=Reflecting People’s Will: Evaluating elections with computer aided simulations|url=https://www.degruyter.com/document/doi/10.1515/openps-2021-0021/html|journal=Open Political Science|language=en|volume=4|issue=1|pages=228–237|doi=10.1515/openps-2021-0021|issn=2543-8042|quote=Instant runoff corrects for the spoiler effect to some extent and reduces strategic voting, however, centre squeeze is a real issue in a three legged race. With two dominant parties, it works well in that it establishes a clearer winner than plurality elections. It has however been observed that the long term end results are likely to be similar, with the same major parties and elimination of smaller parties, similar to plurality voting (but to a lesser extent) as has been witnessed in the Australian elections.}}</ref><ref name=":4" /><ref name=":12">{{Cite book|last=Poundstone, William.|title=Gaming the vote : why elections aren't fair (and what we can do about it)|date=2013|publisher=Farrar, Straus and Giroux|isbn=9781429957649|pages=168, 197, 234|oclc=872601019|quote=IRV is subject to something called the "center squeeze." A popular moderate can receive relatively few first-place votes through no fault of her own but because of vote splitting from candidates to the right and left.}}</ref>
Systems that can do either well or poorly in a center squeeze situation include most [[graded Bucklin]] systems, [[Approval voting]],<ref name=":3" /> and [[
Systems that generally do well with center squeeze include [[Condorcet method|Condorcet systems]]. Some people suggest that a center squeeze scenario could become an opportunity for one of the wings to use burial strategy and create an artificial [[Condorcet paradox|Condorcet cycle]]. However,
===Primary system===
Center squeeze is also a feature of two-party systems which use a [[primary election|primary]] to select candidates. In this case, the two parties tend to separate ideologically, and a "center" candidate, ideologically between the two, would find themselves unable to win a primary against another candidate closer to the centroid of the party. The center candidate would win in any one-on-one vote over the whole voting population, but will not win in the subset of the population represented by a party.
== Effect of strategy ==
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3-candidate example for center squeeze under [[Condorcet]]:
{{ballots|
48: A>B
5: B
47: C>B▼
}}
▲47 C>B
When ignoring C, the votes become 52 voters preferring B to 48 preferring A. If ignoring A instead, the votes become 53 to 47 B to C. So in both directions, the center candidate is preferred by a majority, and thus is the [[Condorcet winner]].
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[[Category:Center squeeze]]
[[Category:Voter strategy]]
[[Category:Political spectrum]]
[[Category:Centrism]]
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