Semi-proportional representation

Social choice and electoral systems
A joint Politics and Economics series

Social choice Mechanism design Comparative politics Comparison List (By country)
Single-winner methods Single vote Plurality rule First preference plurality (FPP) General ticket Majority rule Two-round Nonpartisan primary Partisan primary Instant-runoff UK: Alternative vote (AV) US: Ranked-choice (RCV) Supermajority Consensus Unanimity Condorcet methods Condorcet-IRV Round-robin voting Minimax Kemeny Schulze Ranked pairs Maximal lottery Positional voting Plurality (el. IRV) Borda count (el. Baldwin, ) Antiplurality (el. Coombs) Cardinal voting Score voting Approval voting STAR voting Median voting Majority judgment Graduated Median voting rule Bucklin voting
Proportional representation Party-list Apportionment Highest averages Largest remainders National remnant Biproportional List type Closed list Localized list Open list Free list No 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 Plurality block 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 Apportionment paradox 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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Semi-proportional representation characterizes multi-winner electoral systems which allow some representation of smaller parties or candidates, but produce results that do not always reflect the strength of the competing political forces in a way that is proportional to the shares of the votes they receive. Semi-proportional voting systems are between proportional systems like party-list proportional representation or single transferable vote and winner-take-all systems. Examples of semi-proportional systems include the single non-transferable vote, limited voting, and parallel voting.

There are different measures of proportionality, and no objective threshold, so opinions differ on what constitutes a semi-proportional system, a non-proportional system and a proportional system.