Supplementary Vote

Supplementary Vote
Tomruen at English Wikipedia · Public domain · source
Name	Supplementary Vote
Type	majoritarian
Introduced	20th century
Used in	United Kingdom, Sri Lanka, Nigeria
Ballot	preferential with two preferences
Counting	elimination

Supplementary Vote

The Supplementary Vote is an electoral method used for single-winner contests in which electors record a first and a second preference. It is employed in various United Kingdom mayoral contests, some local government contests, and has been compared with systems used in jurisdictions such as Australia, New Zealand, and Ireland. Advocates and critics have debated the method alongside debates about electoral reform, voting theory, and landmark cases such as the 1998 Greater London Authority referendum.

Introduction

The Supplementary Vote was developed as a simplified preferential system to replace plurality systems in high-profile single-seat elections, aiming to produce winners with broader support while retaining relatively simple ballots. Prominent political figures and institutions including Tony Blair, Ken Livingstone, Boris Johnson, Labour Party, Conservative Party, Liberal Democrats, Electoral Commission and think tanks such as the Institute for Public Policy Research have engaged with debates over its adoption. Comparative scholarship situates it among alternatives advocated by reformers like John H. Humphreys and commentators referenced in reports by bodies including the House of Commons and House of Lords.

Method of Voting

Under the system, electors mark a first preference and may mark one additional preference as a second choice on the ballot paper. Ballot design discussions reference precedents from ballots used in elections involving figures such as Sadiq Khan, George Galloway, Rishi Sunak, David Cameron, Gordon Brown and procedural guidance from institutions such as the Electoral Commission. Comparative methodological literature cites systems implemented in contexts like the Australian House of Representatives, the Irish presidential election, and the New Zealand MMP debates when contrasting ballot simplicity, voter comprehension, and exhaustion rates.

Counting and Vote Transfer Procedure

Counting begins by tallying first-preference votes; if a candidate secures an absolute majority, they are declared elected. If no candidate exceeds 50 percent, all but the top two candidates are eliminated and second-preference markings on ballots for eliminated candidates are examined and transferred to the remaining top two if applicable. The procedure appears in official counting rules debated in proceedings of bodies including the Greater London Authority, the City of London Corporation, the Independent Commission on the Voting System and referenced in judgments such as those from the High Court of Justice in election litigation. Comparative counting procedures relate to algorithms studied by scholars who analyze outputs in relation to systems like Instant-runoff voting, Two-round system, and Approval voting.

History and Adoption

Origins of the Supplementary Vote are traced through reform efforts in the late 20th century and early 21st century, intersecting with campaigns led by actors including Tony Blair and policy proposals from the Labour Party and Liberal Democrats. Notable milestones include the adoption for mayoral contests in London, the use in mayoral elections across English cities, and discussion in national reviews such as the Jenkins Commission style inquiries and parliamentary debates in the House of Commons and House of Lords. Internationally, analogous preferential or two-stage systems were considered or adopted in countries like Sri Lanka, Nigeria, and municipal reforms in parts of Canada.

Advantages and Criticisms

Proponents argue the system reduces vote-splitting, encourages coalition-building among parties such as Labour Party, Conservative Party, Green Party, and the Liberal Democrats, and produces winners with wider acceptability. Supporters include voices in the Electoral Reform Society and some members of the House of Lords. Critics, including commentators in newspapers such as the Times (London), Guardian (London), and academics from institutions like Oxford University, Cambridge University, and London School of Economics argue the system limits voter expression compared with full preferential systems and can produce non-monotonic outcomes examined in literature referencing work by Kenneth Arrow, Amartya Sen, and Maurice D. Sheppard. Electoral law scholars have highlighted concerns about ballot exhaustion, tactical voting, and representativeness in analyses produced for bodies like the Electoral Commission and reports to the House of Commons.

Variants and Comparisons

Variants modify the number of preferences allowed or the elimination threshold; some proposals permit three or more supplementary preferences or introduce weighting rules used in experiments cited by researchers at University College London, University of Oxford, and Massachusetts Institute of Technology. The system is commonly compared with Instant-runoff voting (used in Australian lower house contests), the Two-round system (used in French presidential elections and some Latin American contests), Approval voting (advocated by reformers such as Harold F.), and proportional adaptations like Single transferable vote used in elections in Ireland and Malta. Comparative empirical studies reference contests involving figures like Sadiq Khan, Boris Johnson, Ken Livingstone, and municipal elections in Manchester, Birmingham, and Liverpool.

Notable Elections Using the System

Notable uses include multiple mayoral elections in London involving candidates such as Ken Livingstone, Boris Johnson, and Sadiq Khan, combined with high-profile contests in cities including Manchester, Birmingham, Leeds, and Liverpool. Internationally, similar preferential or two-stage systems have been used in presidential and mayoral contests in jurisdictions including Sri Lanka and local elections in parts of Nigeria. Election analyses and post-election reports from institutions like the Electoral Commission and academic centers at London School of Economics and University College London provide detailed case studies.

Category:Electoral systems