Coexistence (electoral systems)

Social choice and electoral systems
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Social choice Mechanism design Comparative politics Comparison List (By country)
Single-winner methods Single vote – plurality methods First preference plurality (FPP) Two-round (US: Jungle primary) Partisan primary Instant-runoff UK: Alternative vote (AV) US: Ranked-choice (RCV) Party block voting Plurality block voting Condorcet methods Condorcet-IRV Round-robin voting Minimax Kemeny Schulze Ranked pairs Maximal lottery Positional voting Plurality (el. IRV) Borda count (el. Baldwin, Mdn. Bucklin) Antiplurality (el. Coombs) Cardinal voting Score voting Approval voting Majority judgment STAR voting
Proportional representation Party-list Apportionment Highest averages Largest remainders National remnant Biproportional List type Closed list Open list Panachage List-free PR Localized list Quota-remainder methods Single transferable vote (Hare, Droop) Schulze STV CPO-STV Quota Borda Approval-based committees Thiele's method Phragmen's method Expanding approvals rule Method of equal shares Fractional social choice Direct representation Interactive representation Liquid democracy Fractional approval voting Maximal lottery Random ballot Semi-proportional representation Cumulative SNTV Limited voting
Mixed systems By results of combination Mixed-member majoritarian Mixed-member proportional By mechanism of combination Non-compensatory Parallel (superposition) Coexistence Conditional Fusion (majority bonus) Compensatory Seat linkage system UK: 'AMS' NZ: 'MMP' Vote linkage system Negative vote transfer Mixed ballot Supermixed systems Dual-member proportional Rural–urban proportional Majority jackpot By ballot type Single vote Double simultaneous vote Dual-vote
Paradoxes and pathologies Spoiler effects Spoiler effect Cloning paradox Frustrated majorities paradox Center squeeze Pathological response Perverse response Best-is-worst paradox No-show paradox Multiple districts paradox Strategic voting Lesser evil voting Exaggeration Truncation Turkey-raising Wasted vote Paradoxes of majority rule Tyranny of the majority Discursive dilemma Conflicting majorities paradox
Social and collective choice Impossibility theorems Arrow's theorem Majority impossibility Moulin's impossibility theorem McKelvey–Schofield chaos theorem Gibbard's theorem Positive results Median voter theorem Condorcet's jury theorem May's theorem Condorcet dominance theorems Harsanyi's utilitarian theorem VCG mechanism Quadratic voting
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In political science, coexistence^[1] involves different voters using different electoral systems depending on which electoral district they belong to.^[2] This is distinct from other mixed electoral systems that use parallel voting (superposition) or compensatory voting. For example, the rural-urban proportional (RUP) proposal for British Columbia involved the use of a fully proportional system of list-PR or STV in urban regions, combined with MMP in rural regions.^[3]

Coexistence of electoral systems exist in multiple countries, like the Democratic Republic of the Congo and Panama, as well as for elections of the European Parliament.^{[citation needed]} Historically, variants have been used in Iceland (1946–1959), Niger (1993, 1995) and Madagascar (1998).^[4]

Type	System	Example(s) for use
Coexistence	e.g. FPTP/SMP in single-member districts, list-PR in multi-member districts	Democratic Republic of the Congo, Panama
Supermixed	e.g. FPTP/SMP in single-member districts, conditional party block voting in multi-member districts	Cameroon, Chad
	Rural-urban proportional representation (RUP)	Denmark (formerly), Iceland (formerly)
	Seat linkage compensatory mixed system (MMP) and FPTP in special constituencies	Bolivia

Coexistence (electoral systems)

References

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