View source for Gallagher index

{{short description|Measure of electoral disproportionality}}
[[File:Gallagher index map robinson.svg|alt=|thumb|Map of Gallagher index for latest election as of September 2024
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The '''Gallagher index''' measures an electoral system's relative [[Proportional representation|disproportionality]] between votes received and seats in a legislature.<ref>{{cite report |author=Special Committee on Electoral Reform (a Canadian Parliamentary Committee) |date=December 1, 2016 |title= Report 3: Strengthening Democracy in Canada : Principles, Process and Public Engagement for Electoral Reform  |url=http://www.parl.gc.ca/HousePublications/Publication.aspx?Language=e&Mode=1&Parl=42&Ses=1&DocId=8655791&File=177#50 |publisher=Parliament of Canada |page=69 (or p. 83 in PDF search) |access-date=December 26, 2016 |quote=One tool that has been developed to measure an electoral system's relative disproportionality between votes received and seats allotted in a legislature is the Gallagher Index, which was developed by Michael Gallagher (who appeared before the Committee).}}</ref><ref>{{cite news|last1=O'Malley|first1=Kady|title=Read the full electoral reform committee report, plus Liberal and NDP/Green opinions|url=https://ottawacitizen.com/news/politics/read-the-full-electoral-reform-committee-report-plus-liberal-and-ndpgreen-opinions|access-date=December 26, 2016|work=Ottawa Citizen|publisher=Ottawa Citizen|date=December 1, 2016}}</ref> As such, it measures the difference between the percentage of votes each party gets and the percentage of seats each party gets in the resulting legislature, and it also measures this disproportionality from all parties ''collectively'' in any one given election. That collective disproportionality from the election is given a precise score, which can then be used in comparing various levels of proportionality among various elections from various [[electoral systems]].<ref>This is discussed in simple English at {{cite web|title=Gallagher Index Made Easy|url=http://gallagherindex.blogspot.ca/|date=2016-12-31}}</ref> The Gallagher index is a statistical analysis methodology utilised within [[political science]], notably the branch of [[psephology]].

[[Michael Gallagher (academic)|Michael Gallagher]], who created the index, referred to it as a "least squares index", inspired by the [[residual sum of squares|sum of squares of residuals]] used in the method of [[least squares]]. The index is therefore commonly abbreviated as "LSq" even though the measured allocation is not necessarily a least squares fit. The Gallagher index is computed by taking the [[square root]] of half the [[summation|sum]] of the squares of the difference between percent of votes (<math>V_i</math>) and percent of seats (<math>S_i</math>) for each of the [[political parties]] (<math>i=1,\ldots,n</math>).{{sfn|Gallagher|1991|pp=33–51}}

: <math>\mathrm{LSq} = \sqrt{ \frac{1}{2} \sum_{i=1}^n ( V_i-S_i ) ^2}</math>&nbsp;&nbsp;{{sfn|Gallagher|1991|p=40}}

The division by 2 gives an index whose values range between 0 and 100. The larger the differences between the percentage of the votes and the percentage of seats summed over all parties, the larger the Gallagher index. The larger the index value the larger the disproportionality and vice versa. Michael Gallagher included "other" parties as a whole category, and [[Arend Lijphart]] modified it, excluding those parties. Compared to the [[Loosemore–Hanby index]], the Gallagher index is more sensitive to large discrepancies.{{sfn|Gallagher|1991|p=41}} Other indices measuring the proportionality between seat share and party vote share are the [[Loosemore–Hanby index]], [[Rae index]], and the [[Sainte-Laguë Index]].
[[File:Comparison of the Gallagher Index of Greece and selected countries.svg|thumb|300x300px|Comparison of Gallagher indices of various countries since 1945]]

==History==
The first publication of the use of [[least squares]] in measuring the dis-proportionality of election outcomes was by Michael Gallagher in 1991<ref name="data"/> in which he writes: "These [election] indices were originally outlined in Markku Laakso and Rein Taagepera, ‘ “Effective” number of parties: a measure with application to west Europe’, ''Comparative Political Studies'' 12:1 (1979), pp. 3–27 (effective number of parties), and Michael Gallagher, ‘Proportionality, disproportionality and electoral systems’, ''Electoral Studies'' 10:1 (1991), pp. 33–51 (least squares index)."

== Application in Canada ==
The Gallagher index gained considerable attention in Canada in December 2016 in the context of efforts to reform Canada's electoral system.<ref>{{cite news|last1=Cash|first1=Colby|title=Colby Cosh: Did Maryam Monsef actually read the whole electoral reform report?|url=http://news.nationalpost.com/full-comment/colby-cosh-did-maryam-monsef-actually-read-the-whole-electoral-reform-report|access-date=10 December 2016|work=National Post|date=December 2, 2016}}</ref><ref>{{cite news|last1=Wherry|first1=Aaron|title=Minister 'disappointed' as electoral reform committee recommends referendum on proportional representation|url=http://www.cbc.ca/news/politics/wherry-electoral-reform-committee-1.3866879|access-date=10 December 2016|work=CBC News|date=December 1, 2016}}</ref> The [[Canadian House of Commons Special Committee on Electoral Reform|Special Committee on Electoral Reform]] (a [[Parliament of Canada|Parliamentary]] Committee) recommended "that the Government should, as it develops a new electoral system, use the Gallagher index in order to minimize the level of distortion between the popular will of the electorate and the resultant seat allocations in Parliament." The committee recommended that "the government should seek to design a system that achieves a Gallagher score of 5 or less."<ref>{{cite news|last1=O'Malley|first1=Kady|title=Read the full electoral reform committee report, plus Liberal and NDP/Green opinions|url=https://ottawacitizen.com/news/politics/read-the-full-electoral-reform-committee-report-plus-liberal-and-ndpgreen-opinions|access-date=10 December 2016|work=Ottawa Citizen|publisher=Ottawa Citizen|date=December 1, 2016}}</ref><ref>{{cite web|title=Is Canada Fair?|url=https://iscanadafair.ca/|website=Measuring Unfairness — Calculating Canada's Gallagher Index|at=(This website includes the Gallagher Index in adjustable table format. It initially shows the data for Canada's 2015 federal election, but some variables in some table cells are adjustable by the visitor to the website, and then the rest of the table is automatically adjusted to reflect this visitor's new input.)| access-date=10 December 2016}}</ref> 

== Examples of calculating disproportionality ==
===Canada===
In the 2015 Canadian federal election, the Gallagher index was 12.02, where 0 would be a perfectly proportional election outcome.<ref>The rules for federal elections in Canada require that certain provinces always get a certain quantity of seats – on a province by province basis. If so, then Byron Weber Becker proposed that the Gallagher index for Canada ought to ALSO reflect that.  In other words, the Gallagher data should be collected on a province by province basis; and the Gallagher score should be calculated on a province by province basis. Only after that is done, can we then add up all of those provincial scores and then average them out to get the true national "composite Gallagher index" score. If we do that, then the illustrated table calculation of 12 for Canada is incorrect. It should instead show a "composite Gallagher index" of 17.1. Byron Weber Becker developed this "composite" index. See citation here: {{cite report |author=Special Committee on Electoral Reform (a Canadian Parliamentary Committee) |date=December 1, 2016 |title= Report 3: Strengthening Democracy in Canada : Principles, Process and Public Engagement for Electoral Reform  |url=https://www.ourcommons.ca/documentviewer/en/42-1/ERRE/report-3/page-243#72|publisher=Parliament of Canada |page=69 (or p. 83 in PDF search) |access-date=April 24, 2024 |quote=...Professor Becker developed the “Gallagher Index Composite” for the Committee’s study...}}</ref>
{{Gallagher index
|election = [[2015 Canadian federal election]]
|side = none
|size = 100
|explanation = no
|color1 = {{Canadian party colour|CA|Liberal}}
|party1 = Liberal
|votes1 = 39.47
|seats1 = 54.44
|color2 = {{Canadian party colour|CA|Conservative}}
|party2 = Conservatives
|votes2 = 31.89
|seats2 = 29.29
|color3 = {{Canadian party colour|CA|NDP}}
|party3 = New Democratic
|votes3 = 19.71
|seats3 = 13.02
|color4 = {{Canadian party colour|CA|BQ}}
|party4 = Bloc Québecois
|votes4 = 4.66
|seats4 = 2.96
|color5 = {{Canadian party colour|CA|Green}}
|party5 = Green
|votes5 = 3.45
|seats5 = 0.29
|color6 = {{Canadian party colour|CA|Others}}
|party6 = Other
|votes6 = 0.82
|seats6 = 0
|party7 = Error example
|votes7 = Values such as 2%; 2,14; text; null/blank
|seats7 = Row will not be shown for any of these values
}}

=== Australia ===
This table uses for example the [[2012 Queensland state election]], one of the largest landslides in Australian electoral history. Though Australia and New Zealand have somewhat similar political histories,{{cn|date=May 2025}} Australia uses [[Instant-runoff voting|preferential voting]] in [[Single-member district]]s for [[Australian House of Representatives|Commonwealth House of Representative]] and most [[Parliaments of the Australian states and territories|state and territory Legislative Assembly]] elections, which tends to result in far less proportionality compared to New Zealand's MMP system (or other proportional electoral systems), especially for larger minor parties, such as [[Australian Greens|The Greens]] or, historically, the [[Australian Democrats]]. The 2012 Queensland election had an extremely high Gallagher Index, at 31.16, due to the massive landslide in seats for the victorious [[Liberal National Party of Queensland|LNP]]. The LNP gained 88% of the seats with less than 50% of the vote. Most recent Australian state and federal elections however score between 10 and 12.
{{Gallagher index
|election = [[2012 Queensland state election]]
|side = none
|size = 100
|explanation = no
|color1 = {{party color|Liberal National Party of Queensland}}
|party1 = [[Liberal National Party of Queensland|Liberal National]]
|votes1 = 49.65
|seats1 = 87.64
|color2 = {{party color|Australian Labor Party}}
|party2 = [[Australian Labor Party (Queensland Branch)|Labor]]
|votes2 = 26.66
|seats2 = 7.87
|color3 = {{party color|Katter's Australian Party}}
|party3 = [[Katter's Australian Party|Katter]]
|votes3 = 11.53
|seats3 = 2.25
|color4 = {{party color|Australian Greens}}
|party4 = [[Queensland Greens|Greens]]
|votes4 = 7.53
|seats4 = 0
|color5 = {{party color|Others}}
|party5 = Other
|votes5 = 1.47
|seats5 = 0
|color6 = {{party color|Independent}}
|party6 = [[Independent politician|Independent]]
|votes6 = 3.16
|seats6 = 2.25
}}

=== EU ===
The 7 [[political groups of the European Parliament]] instead of the 203 political parties<ref>{{cite web|url=https://www.europarl.europa.eu/RegData/etudes/BRIE/2022/698880/EPRS_BRI(2022)698880_EN.pdf| title=European Parliament: Facts and Figures |access-date=13 February 2023}}</ref> allow a concise calculation of disproportionality between votes and seats. The Gallagher index for the European Parliament is 7.87.
{{Gallagher index
|election = [[2019 European Parliament election]]<ref>{{cite web|url=https://www.election-results.eu/tools/comparative-tool/ |title=2019 European election results – Comparative tool |publisher=[[European Parliament]] |access-date=5 July 2019}}</ref>
|side = none
|size = 100
|explanation = no
|color1 = {{party color|European People's Party group}}| 
|party1 = [[European People's Party group|EPP]]
|votes1 = 20.80
|seats1 = 24.23
|color2 = {{party color|Progressive Alliance of Socialists and Democrats}}
|party2 = [[Progressive Alliance of Socialists and Democrats|S&D]]
|votes2 = 17.88
|seats2 = 20.51
|color3 = {{party color|Renew Europe}}
|party3 = [[Renew Europe|RE]]
|votes3 = 12.01
|seats3 = 14.38
|color4 = {{party color|Greens–European Free Alliance}}
|party4 = [[Greens–European Free Alliance|G/EFA]]
|votes4 = 10.04
|seats4 = 9.85
|color5 = {{party color|Identity and Democracy}}
|party5 = [[Identity and Democracy|ID]]
|votes5 = 10.59
|seats5 = 9.72
|color6 = {{party color|European Conservatives and Reformists}}
|party6 = [[European Conservatives and Reformists Group|ECR]]
|votes6 = 7.17
|seats6 = 8.26
|color7 = {{party color|European United Left–Nordic Green Left}}
|party7 = [[European United Left–Nordic Green Left|GUE/NGL]]
|votes7 = 5.16
|seats7 = 5.46
|color8 = {{party color|Non-Inscrits}}
|party8 = [[Non-Inscrits|NI]]
|votes8 = 6.52
|seats8 = 7.59
|party9 = [[Wasted vote]]
|votes9 = 9.82
|seats9 = 0.00}}

=== Sweden ===
The disproportionality of the [[2022 Swedish general election]] was 0.64 according to the Gallagher index, which is extremely low by international standards (resulting in almost perfectly proportional seat allocations), due to Sweden's use of the [[Webster/Sainte-Laguë method#Modified Sainte-Laguë method|modified Sainte-Laguë method]] in elections to the [[Riksdag]].

=== Republic of Ireland ===
The disproportionality of the [[2020 Irish general election]] was 1.96 according to the Gallagher index. The Republic of Ireland uses the [[single transferable vote]] (STV) system with [[Droop quota]] in elections to the [[Dáil Éireann]].

=== United States ===
This table uses the aggregate results of the [[2012 United States House of Representatives elections|2012 elections to the United States House of Representatives]].  These 435 [[Single-member district|single-seat elections]] are [[first-past-the-post voting|winner-take-all]], which would tend to create disproportionate results, but this is moderated by the extremely high share of votes obtained by the [[two-party system|two major parties]]—more than 96%, likely in part caused by fears of [[Wasted vote|wasted votes]] and [[vote splitting]]. The Gallagher index ignores the effect of the primaries on the proportionality.
{{Gallagher index
|election = [[2012 United States House of Representatives elections]]
|side = none
|size = 100
|explanation = no
|color1 = {{party color|Republican Party (United States)}}
|party1 = [[Republican Party (United States)|Republican Party]]
|votes1 = 47.66
|seats1 = 53.80
|color2 = {{party color|Democratic Party (United States)}}
|party2 = [[Democratic Party (United States)|Democratic Party]]
|votes2 = 48.77
|seats2 = 44.20
|color3 = {{party color|Libertarian Party (United States)}}
|party3 = [[Libertarian Party (United States)|Libertarian Party]]
|votes3 = 1.11
|seats3 = 0
|color4 = {{party color|Others}}
|party4 = [[Independent politician|Independents]] and [[Third party (United States)|minor parties]]
|votes4 = 1.01
|seats4 = 0
|color5 = {{party color|Green Party of the United States}}
|party5 = [[Green Party (United States)|Green Party]]
|votes5 = 0.31
|seats5 = 0
|color6 = darkgray
|party6 = Others
|votes6 = 1.13
|seats6 = 0
}}

=== United Kingdom ===
The 2024 general election in the United Kingdom was the most disproportional in modern British history.<ref name="data2">{{cite web |last=Gallagher |first=Michael |title=Election Indices |url=https://www.tcd.ie/Political_Science/about/people/michael_gallagher/ElSystems/Docts/ElectionIndices.pdf |url-status=live |archive-url=http://web.archive.org/web/20240729233608/https://www.tcd.ie/Political_Science/about/people/michael_gallagher/ElSystems/Docts/ElectionIndices.pdf |archive-date=29 July 2024 |access-date=29 July 2024}}</ref> The Liberal Democrats recorded their best ever seat result (72), despite receiving only around half the votes they did in [[2010 United Kingdom general election|2010]],<ref name="The Guardian">{{Cite web |date=5 July 2024 |title=The Guardian view on Labour's landslide: becoming the change the country needs |url=https://www.theguardian.com/commentisfree/article/2024/jul/05/the-guardian-view-on-labours-landslide-becoming-the-change-the-country-needs |access-date=5 July 2024 |work=[[The Guardian]]}}</ref> and fewer votes overall than Reform, although the party's seat share was again lower than its share of the vote. Advocacy group [[Make Votes Matter]] found that 58% of voters did not vote for their elected MP. Make Votes Matter spokesman Steve Gilmore, [[Electoral Reform Society]] chief [[Darren Hughes]], Reform UK leader Nigel Farage and the Green Party of England and Wales co-leader Adrian Ramsay were among the figures that called for electoral reform in the wake of the election. The campaigners said it was the "most disproportionate election in [British] history".<ref>{{Cite web |last=Topping |first=Alexandra |date=8 July 2024 |title='Disproportionate' UK election results boost calls to ditch first past the post |url=https://www.theguardian.com/politics/article/2024/jul/08/disproportionate-uk-election-results-boost-calls-to-ditch-first-past-the-post |access-date=8 July 2024 |work=[[The Guardian]]}}</ref><ref>{{Cite web |date=5 July 2024 |title=Biggest-ever gap between number of votes and MPs hits Reform and Greens |url=https://www.bbc.co.uk/news/articles/c886pl6ldy9o |access-date=8 July 2024 |work=[[BBC News]]}}</ref>{{Gallagher index
| election = [[2024 United Kingdom general election]]
| side = none
| size = 100
| explanation = no
| color1 = {{party color|Labour Party (UK)}}
| party1 = [[Labour Party (UK)|Labour]]
| votes1 = 33.70
| seats1 = 63.23
| color2 = {{party color|Conservative Party (UK)}}
| party2 = [[Conservative Party (UK)|Conservative]]
| votes2 = 23.70
| seats2 = 18.62
| color3 = {{party color|Reform UK}}
| party3 = [[Reform UK]]
| votes3 = 14.29
| seats3 = 0.77
| color4 = {{party color|Liberal Democrats (UK)}}
| party4 = [[Liberal Democrats (UK)|Liberal Democrats]]
| votes4 = 12.22
| seats4 = 11.08
| color5 = {{party color|Green Party of England and Wales}}
| party5 = [[Green Party of England and Wales|Green]]
| votes6 = 1.96
| seats6 = 0.92
| color6 = {{party color|Independent politician}}
| party6 = [[Independent politician|Independents]]
| votes7 = 7.74
| seats7 = 4.92
| color7 = darkgray
| party7 = Others
| votes5 = 6.39
| seats5 = 0.46
}}

== Countries ==
{{Dynamic list}}
{{Sticky header}}
{| class="wikitable sortable sticky-header"
|+Gallagher indices for individual countries. Only the last available index for each country is shown.<ref name="data">{{cite web|title=Election Indices |last=Gallagher |first=Michael |url=https://www.tcd.ie/Political_Science/about/people/michael_gallagher/ElSystems/Docts/ElectionIndices.pdf |access-date=29 July 2024 |url-status=live |archive-url=http://web.archive.org/web/20240729233608/https://www.tcd.ie/Political_Science/about/people/michael_gallagher/ElSystems/Docts/ElectionIndices.pdf |archive-date=29 July 2024 }}</ref> 
! Country !! Year !! Gallagher Index
|-
| {{flaglist|Albania}}	||	[[2021 Albanian parliamentary election|2021]]	||	4.57
|-
| {{flaglist|Algeria}}	||	[[2021 Algerian parliamentary election|2021]]	||	21.20
|-
| {{flaglist|Andorra}}	||	[[2023 Andorran parliamentary election|2023]]	||	16.47
|-
| {{flaglist|Angola}}	||	[[2022 Angolan general election|2022]]	||	4.32
|-
| {{flaglist|Antigua and Barbuda}}	||	[[2023 Antiguan general election|2023]]	||	8.79
|-
| {{flaglist|Argentina}}	||	[[2023 Argentine general election|2023]]	||	5.14
|-
| {{flaglist|Armenia}}	||	[[2021 Armenian parliamentary election|2021]]	||	10.74
|-
| {{flaglist|Australia}}	||	[[2022 Australian federal election|2022]]	||	16.72
|-
| {{flaglist|Austria}}	||	[[2024 Austrian legislative election|2024]]	||	3.21
|-
| {{flaglist|Bahamas}}	||	[[2021 Bahamian general election|2021]]	||	25.01
|-
| {{flaglist|Barbados}}	||	[[2022 Barbadian general election|2022]]	||	28.92
|-
| {{flaglist|Belgium}}	||	[[2024 Belgian federal election|2024]]||	3.83
|-
| {{flaglist|Belize}}	||	[[2025 Belizean general election|2025]]	||	20.92
|-
| {{flaglist|Benin}}	||	[[2023 Beninese parliamentary election|2023]]	||	9.08
|-
| {{flaglist|Bermuda}}	||	[[2025 Bermudian general election|2025]]	||	16.30
|-
| {{flaglist|Bhutan}}	||	[[2023–24 Bhutanese National Assembly election|2023-24]]	||	24.70
|-
| {{flaglist|Bolivia}}	||	[[2020 Bolivian general election|2020]]	||	2.60
|-
| {{flaglist|Bosnia and Herzegovina}}	||	[[2022 Bosnian general election|2022]]	||	5.30
|-
| {{flaglist|Botswana}}	||	[[2019 Botswana general election|2019]]	||	12.26
|-
| {{flaglist|Brazil}}	||	[[2022 Brazilian general election|2022]]	||	3.53
|-
| {{flaglist|Bulgaria}}	||	[[2023 Bulgarian parliamentary election|2023]]	||	3.77
|-
| {{flaglist|Burkina Faso}}	||	[[2020 Burkinabè general election|2020]]	||	8.16
|-
| {{flaglist|Cabo Verde}}	||	[[2021 Cape Verdean parliamentary election|2021]]	||	3.54
|-
| {{flaglist|Canada}}	||	[[2021 Canadian federal election|2021]]	||	13.39
|-
| {{flaglist|Chile}}	||	[[2021 Chilean general election|2021]]	||	9.58
|-
| {{flaglist|Colombia}} 	||	[[2022 Colombian parliamentary election|2022]]	||	4.60
|-
| {{flaglist|Costa Rica}}	||	[[2022 Costa Rican general election|2022]]	||	8.26
|-
| {{flaglist|Croatia}}	||	[[2024 Croatian parliamentary election|2024]]||	7.04
|-
| {{flaglist|Cyprus}}	||	[[2021 Cypriot legislative election|2021]]	||	6.44
|-
| {{flaglist|Czech Republic}}	||	[[2021 Czech parliamentary election|2021]]	|| 10.34
|-
| {{flaglist|Denmark}}	||	[[2022 Danish general election|2022]]	||	1.13
|-
| {{flaglist|Dominica}}	||	[[2022 Dominican general election|2022]]	||	6.55
|-
| {{flaglist|Dominican Republic}}	||	[[2020 Dominican Republic general election|2020]]	||	7.32
|-
| {{flaglist|El Salvador}}	||	[[2024 Salvadoran general election|2024]]||	15.02
|-
| {{flaglist|Estonia}}	||	[[2023 Estonian parliamentary election|2023]]	||	4.66
|-
| {{flaglist|EU}}	||	[[2019 European Parliament election|2019]]	||  7.87
|-
| {{flaglist|Faeroe Islands}}	||	[[2019 Faroese general election|2019]]	||	1.66
|-
| {{flaglist|Fiji}}	||	[[2022 Fijian general election|2022]] ||	4.75
|-
| {{flaglist|Finland}}	||	[[2023 Finnish parliamentary election|2023]]	||	3.99
|-
| {{flaglist|France}}	||	[[2024 French legislative election|2024]]||	7.79
|-
| {{flaglist|Gambia}}	||	[[2022 Gambian parliamentary election|2022]]	||	7.93
|-
| {{flaglist|Georgia}}	||	[[2020 Georgian parliamentary election|2020]]	||	8.71
|-
| {{flaglist|Germany}}	||	[[2021 German federal election|2021]]	||	3.48
|-
| {{flaglist|Ghana}}	||	[[2020 Ghanaian general election|2020]]	||	2.64
|-
| {{flaglist|Gibraltar}}	||	[[2023 Gibraltar general election|2023]]	||	2.45
|-
| {{flaglist|Greece}}	||	[[June 2023 Greek legislative election|2023]]	||	8.97
|-
| {{flaglist|Greenland}}	||	[[2021 Greenlandic general election|2021]]	||	2.75
|-
| {{flaglist|Grenada}}	||	[[2022 Grenadian general election|2022]]	||	7.97
|-
| {{flaglist|Guatemala}}	||	[[2023 Guatemalan general election|2023]]	||	8.85
|-
| {{flaglist|Guinea}}	||	[[2020 Guinean parliamentary election|2020]]	||	2.14
|-
| {{flaglist|Guinea-Bissau}}	||	[[2023 Guinea-Bissau parliamentary election|2023]]	||	10.81
|-
| {{flaglist|Guyana}}	||	[[2020 Guyanese general election|2020]]	||	0.52
|-
| {{flaglist|Honduras}}	||	[[2021 Honduran general election|2021]]	||	6.41
|-
| {{flaglist|Hungary}}	||	[[2022 Hungarian parliamentary election|2022]] || 11.76
|-
| {{flaglist|Iceland}}	||	[[2021 Icelandic parliamentary election|2021]]	||	3.96
|-
| {{flaglist|India}}	||	[[2024 Indian general election|2024]]||	6.98
|-
| {{flaglist|Indonesia}}	||	[[2024 Indonesian general election|2024]]||	4.86
|-
| {{flaglist|Ireland}}	||	[[2020 Irish general election|2020]]	||	2.22
|-
| {{flaglist|Israel}}	||	[[2022 Israeli legislative election|2022]]	||	4.40
|-
| {{flaglist|Italy}}	||	[[2022 Italian general election|2022]]	||	12.37
|-
| {{flaglist|Jamaica}}	||	[[2020 Jamaican general election|2020]]	||	20.62
|-
| {{flaglist|Japan}}	||	[[2021 Japanese general election|2021]]	||	11.43
|-
| {{flaglist|Kosovo}}	||	[[2021 Kosovan parliamentary election|2021]]	||	3.58
|-
| {{flaglist|Latvia}}	||	[[2022 Latvian parliamentary election|2022]]	||	10.65
|-
| {{flaglist|Lesotho}}	||	[[2022 Lesotho general election|2022]]	||	6.03
|-
| {{flaglist|Liberia}}	||	[[2023 Liberian general election|2023]]	||	10.13
|-
| {{flaglist|Liechtenstein}}	||	[[2021 Liechtenstein general election|2021]]	||	5.62
|-
| {{flaglist|Lithuania}}	||	[[2020 Lithuanian parliamentary election|2020]]	||	9.49
|-
| {{flaglist|Luxembourg}}	||	[[2023 Luxembourg general election|2023]]	||	5.96
|-
| {{flaglist|Malawi}}	||	[[2019 Malawian general election|2019]]	||	8.56
|-
| {{flaglist|Malaysia}}	||	[[2022 Malaysian general election|2022]]	||	6.99
|-
| {{flaglist|Malta}}	||	[[2022 Maltese general election|2022]]	||	2.24
|-
| {{flaglist|Mauritius}}	||	[[2024 Mauritian general election|2024]]	||	31.38
|-
| {{flaglist|Mexico}}	||	[[2024 Mexican general election|2024]]||	15.58
|-
| {{flaglist|Moldova}}	||	[[2021 Moldovan parliamentary election|2021]]	||	8.44
|-
| {{flaglist|Monaco}}	||	[[2023 Monegasque general election|2023]] || 10.37
|-
| {{flaglist|Mongolia}} || [[2024 Mongolian parliamentary election|2024]] || 12.84
|-
| {{flaglist|Montenegro}}	||	[[2023 Montenegrin parliamentary election|2023]] || 4.93
|-
| {{flaglist|Morocco}}	||	[[2021 Moroccan general election|2021]]	||	4.18
|-
| {{flaglist|Mozambique}}	||	[[2019 Mozambican general election|2019]]	||	2.45
|-
| {{flaglist|Namibia}}	||	[[2019 Namibian general election|2019]]	||	0.98
|-
| {{flaglist|Nepal}}	||	[[2022 Nepalese general election|2022]]	||	6.02
|-
| {{flaglist|Netherlands}}	||	[[2023 Dutch general election|2023]]	||	1.46
|-
| {{flaglist|New Zealand}}	||	[[2023 New Zealand general election|2023]]	||	2.63
|-
| {{flaglist|Nicaragua}} ||	[[2021 Nicaraguan general election|2021]] || 7.56
|-
| {{flaglist|Niger}}	||	[[2020–21 Nigerien general election|2020-21]]	||	8.10
|-
| {{flaglist|North Cyprus}}	||	[[2022 Northern Cypriot parliamentary election|2022]]	||	7.78
|-
| {{flaglist|North Macedonia}}	||	[[2024 North Macedonian parliamentary election|2024]]||	3.42
|-
| {{flaglist|Northern Ireland}}	||	[[2022 Northern Ireland Assembly election|2022]]	||	7.80
|-
| {{flaglist|Norway}}	||	[[2021 Norwegian parliamentary election|2021]]	||	3.65
|-
| {{flaglist|Pakistan}}	||	[[2024 Pakistani general election|2024]]||	11.41
|-
| {{flaglist|Panama}}	||	[[2024 Panamanian general election|2024]]||	9.77
|-
| {{flaglist|Paraguay}}	||	[[2023 Paraguayan general election|2023]]	||	9.53
|-
| {{flaglist|Peru}}	||	[[2021 Peruvian general election|2021]]	||	14.02
|-
| {{flaglist|Poland}}	||	[[2023 Polish parliamentary election|2023]]	||	6.46
|-
| {{flaglist|Portugal}}	||	[[2024 Portuguese legislative election|2024]]||	5.94
|-
| {{flaglist|Romania}}	||	[[2020 Romanian legislative election|2020]]	||	6.14
|-
| {{flaglist|Russia}}	||	[[2021 Russian legislative election|2021]]	||	17.13
|-
| {{flaglist|Saint Kitts and Nevis}} ||  [[2022 Saint Kitts and Nevis general election|2022]] ||  15.97
|-
| {{flaglist|Saint Lucia}}	||	[[2021 Saint Lucian general election|2021]]	||	28.97
|-
| {{flaglist|Saint Vincent and the Grenadines}}	|| [[2020 Vincentian general election|2020]] || 10.37
|-
| {{flaglist|San Marino}}	||	[[2024 San Marino general election|2024]]||	3.88
|-
| {{flaglist|Sao Tome and Principe}}	||	[[2022 São Toméan parliamentary election|2022]]	||	7.04
|-
| {{flaglist|Scotland}}	||	[[2021 Scottish Parliament election|2021]]    ||	7.03
|-
| {{flaglist|Senegal}}	||	[[2022 Senegalese parliamentary election|2022]]	||	2.73
|-
| {{flaglist|Serbia}}	||	[[2023 Serbian parliamentary election|2023]]	||	3.80
|-
| {{flaglist|Seychelles}}	||	[[2020 Seychellois general election|2020]]	||	15.33
|-
| {{flaglist|Sierra Leone}}	||	[[2023 Sierra Leonean general election|2023]]	||	2.44
|-
| {{flaglist|Singapore}}	||	[[2025 Singaporean general election|2025]]	||	18.27
|-
| {{flaglist|Slovakia}}	||	[[2023 Slovak parliamentary election|2023]]||	7.44
|-
| {{flaglist|Slovenia}}	||	[[2022 Slovenian parliamentary election|2022]]	||	11.49
|-
| {{flaglist|South Africa}}	||	[[2024 South African general election|2024]]||	0.48
|-
| {{flaglist|South Korea}}	||	[[2020 South Korean legislative election|2020]]	||	13.65
|-
| {{flaglist|Spain}}	||	[[2023 Spanish general election|2023]]	||	5.67
|-
| {{flaglist|Sri Lanka}}	||	[[2020 Sri Lankan parliamentary election|2020]]	||	4.54
|-
| {{flaglist|Suriname}}	||	[[2020 Surinamese general election|2020]]	||	8.70
|-
| {{flaglist|Sweden}}	||	[[2022 Swedish general election|2022]]	||	0.64
|-
| {{flaglist|Switzerland}}	||	[[2023 Swiss federal election|2023]]	||	3.60
|-
| {{flaglist|Taiwan}}	||	[[2024 Taiwanese legislative election|2024]]	||	8.19
|-
| {{flaglist|Thailand}}	||	[[2023 Thai general election|2023]]	||	5.51
|-
| {{flaglist|Timor-Leste}}	||	[[2023 East Timorese parliamentary election|2023]]	||	6.06
|-
| {{flaglist|Trinidad and Tobago}}	||  [[2020 Trinidad and Tobago general election|2020]]||	3.55
|-
| {{flaglist|Turkey}}	||  [[2023 Turkish parliamentary election|2023]] ||	3.61
|-
| {{flaglist|Uganda}}	||	[[2021 Ugandan general election|2021]]	||	14.90
|-
| {{flaglist|United Kingdom}}	||	[[2024 United Kingdom general election|2024]]||	23.64
|-
| {{flaglist|United States}}	||	[[2020 United States presidential election|2020]]	||	4.89
|-
| {{flaglist|Uruguay}}	||	[[2019 Uruguayan general election|2019]]	||	1.73
|-
| {{flaglist|Venezuela}}	||	[[2020 Venezuelan parliamentary election|2019]]	||	18.40
|-
| {{flaglist|Wales}}	||	[[2021 Senedd election|2021]]	||	9.36
|-
| {{flaglist|Zambia}}	||	[[2021 Zambian general election|2021]]	||	5.21
|-
| {{flaglist|Zimbabwe}}	||	[[2023 Zimbabwean general election|2023]]	||	6.05
|}

== See also ==
* [[Democracy indices]]
* [[Efficiency gap]]

== Notes ==
{{Reflist|30em}}

== References ==
* {{cite journal |last1=Benoit |first1= Kenneth |year= 2000 |title=Which Electoral Formula Is the Most Proportional? A New Look with New Evidence |journal=Political Analysis |volume=8 |issue=4 |pages=381–388 |doi=10.1093/oxfordjournals.pan.a029822}}
* {{cite journal |last1= Gallagher |first1= Michael |author-link=Michael Gallagher (academic) |year=1991 |title=Proportionality, Disproportionality and Electoral Systems |journal=Electoral Studies |volume= 10 |pages=33–51 |doi=10.1016/0261-3794(91)90004-c}}
* {{cite journal |last1= Gallagher |first1= Michael |year=1992 |title=Comparing Proportional Representation Electoral Systems: Quotas, Thresholds, Paradoxes and Majorities |journal=British Journal of Political Science |volume= 22 |issue= 4 |pages=469–496 |doi=10.1017/s0007123400006499|s2cid= 153414497 }}
* {{cite book |editor-last1= Gallagher |editor-first1= Michael |editor-last2=Mitchell |editor-first2=P |year=2005 |title=The Politics of Electoral Systems | location= [[Oxford]] | publisher= [[Oxford University Press]] |at= Appendix B |isbn =978-0-19-925756-0}}
* {{cite journal |last1= Kestelman |first1= Philip |date=March 1999 |title=Quantifying Representativity |journal=Voting Matters |volume= 10 |url = http://www.votingmatters.org.uk/ISSUE10/P6.HTM |access-date=10 August 2013}}

== External links ==
{{Portal|Politics}}
* [http://gallagherindex.blogspot.ca/2016/12/its-important-and-easy-to-understand.html Gallagher Index Made Easy]
* [https://www.tcd.ie/Political_Science/about/people/michael_gallagher/ElSystems/index.php Michael Gallagher's Electoral Systems web site]
* [https://docs.google.com/document/d/1j86Oylz9IRL_RLQ1CrVNmcxStbxzVXy0NvP10BjrVuI/edit# The Gallagher Index: A Measure of Disproportionality]
* [https://commons.wikimedia.org/wiki/Category:Gallagher_Index Various Gallagher Indexes at Wikimedia Commons]
* [https://iscanadafair.ca/gallagher-index/ Website: Measuring Unfairness — Calculating Canada's Gallagher Index] (This website includes the Gallagher Index in adjustable table format. It initially shows the data for Canada's 2015 federal election, but some variables in some table cells are adjustable by the visitor to the website, and then the rest of the table is automatically adjusted to reflect this visitor's new input).

{{Politics country lists}}

[[Category:Voting theory]]