Purpose & Core Concepts
What an electoral system does
Converts votes into seats/representation
Structures competition among parties/candidates
Shapes government formation and accountability
Key terms
Constituency/District
Single-member district (SMD)
Multi-member district (MMD)
Ballot structure
Candidate-centered vs party-centered
Ranking vs single choice vs multiple votes
Seat allocation
Winner-take-all vs proportional allocation
Allocation formulas (e.g., D’Hondt, Sainte-Laguë, Hare quota)
Electoral threshold
Legal thresholds (e.g., 5%)
Effective thresholds (driven by district magnitude)
District magnitude (M)
Number of seats per district
Higher M generally increases proportionality
Malapportionment & gerrymandering
Strategic boundary drawing
Party system outcomes
Two-party vs multiparty dynamics
Main Families of Electoral Systems
Plurality/Majoritarian Systems
First-Past-the-Post (FPTP) / Plurality in SMD
Two-Round System (Runoff)
Alternative Vote (AV) / Instant-Runoff Voting (IRV)
Block Vote (Plurality in MMD)
Party Block Vote (Winner-take-all in MMD)
Proportional Representation (PR)
Single Transferable Vote (STV)
Mixed systems with proportional elements
Mixed-Member Proportional (MMP)
Parallel / Mixed-Member Majoritarian (MMM)
Semi-proportional / Other
Single Non-Transferable Vote (SNTV)
Systems range from winner-take-all to proportional, with mixed and semi-proportional designs bridging the gap.
How Votes Translate into Seats (Mechanisms)
District-based winners
SMD: highest vote-getter wins (plurality) or majority required (runoff/AV)
MMD: multiple winners via block voting or proportional allocation
Proportional allocation logic
Determine total seats per district or nationwide
Convert vote shares into seat shares using a formula
Apply thresholds and rounding rules
Common PR allocation methods
Largest Remainder
Hare quota: seats = floor(votes/quota) + remainders
Droop quota (often used with STV-like logic)
Highest Averages
D’Hondt (slightly favors larger parties)
Sainte-Laguë (more favorable to mid/smaller parties)
Transfer/Ranking logic
Preference redistribution (AV, STV)
Surplus transfers in STV when a candidate exceeds quota
Elimination and transfer cycles until seats filled
Mixed system logic
Two tiers: district seats + list seats
Compensation rules
MMP: list seats compensate to match overall vote share
Parallel: list seats do not compensate; outcomes less proportional
Plurality/Majoritarian Systems (Detailed)
First-Past-the-Post (FPTP)
Ballot: choose one candidate
Seat rule: candidate with most votes wins the seat
Translation effect
Strong seat bonus for leading party
Many “wasted votes” for losing candidates
Disproportional outcomes common
Typical outcomes
Encourages two major competitors (strategic voting)
Single-party governments more likely
Strengths/Trade-offs
Clear geographic representation
Can under-represent dispersed minorities and smaller parties
Two-Round System (Runoff)
Ballot: choose one candidate (round 1), then round 2 if needed
Seat rule
If no majority in round 1, top candidates proceed (rules vary)
Round 2 majority/plurality decides
Translation effect
Allows voters to coordinate in round 2
Can reduce “spoiler” effect compared with FPTP
Strengths/Trade-offs
Produces majority-backed winners more often
More costly; turnout can drop in round 2
Alternative Vote (AV/IRV)
Seat rule
If no majority of first preferences, eliminate lowest
Transfer votes to next preference until majority
Translation effect
Reduces vote splitting among similar candidates
Still not proportional for legislatures in SMD
Strengths/Trade-offs
Encourages broader appeal
Counting complexity and potential non-intuitive outcomes
Block Vote (MMD plurality)
Ballot: multiple selections up to number of seats
Seat rule: top vote-getters fill seats
Translation effect
Can heavily favor dominant group/party
Often highly disproportional
Party Block Vote
Ballot: choose a party list in an MMD
Seat rule: party with most votes wins all seats
Translation effect
Extreme winner-take-all; strong majoritarian outcomes
Proportional Representation (PR) Systems (Detailed)
Party-List PR
Core idea
Parties win seats roughly in proportion to votes
Uses MMDs or national districts
Closed-list PR
Party determines candidate order
Translation effect: strong party control; proportional seat outcomes
Open-list PR
Voters choose party and/or preferred candidates
Candidate vote totals influence who takes seats
Translation effect: intra-party competition; personal vote incentives
Flexible-list PR
Party order matters but can be altered by preference votes above a threshold
Key design levers shaping representation
District magnitude: higher M increases proportionality
Legal thresholds: higher thresholds reduce small-party representation
Allocation formula: D’Hondt vs Sainte-Laguë impacts party advantage
National vs regional tiers: affects geographic representation
Single Transferable Vote (STV)
Ballot: rank candidates in an MMD
Seat rule
Candidates reach a quota to be elected
Surplus votes transfer according to next preferences
Lowest candidates eliminated with transfers until seats filled
Translation effect
Proportional-ish outcomes, especially with higher M
Stronger voter choice among candidates
Strengths/Trade-offs
Balances proportionality and local representation
Complex count; larger ballots can be demanding
PR systems prioritize proportional seat-vote outcomes, with list design and district magnitude strongly shaping party and candidate incentives.
Mixed Electoral Systems (Detailed)
Mixed-Member Proportional (MMP)
Structure
Two votes often used: district candidate + party list
District seats elected by FPTP/SMD
List seats allocated to make overall seat shares proportional to party votes
Translation effect
Overall proportionality high (depends on design and size of list tier)
Overhang seats may occur if a party wins more district seats than entitlement
Strengths/Trade-offs
Keeps local MPs while preserving proportionality
Complexity; coalition governments more common
Parallel / Mixed-Member Majoritarian (MMM)
Structure
District tier and list tier run independently
List seats do not compensate for district disproportionality
Translation effect
Less proportional than MMP
Larger parties can gain a combined advantage
Strengths/Trade-offs
Simpler than MMP; maintains some proportional element
Can still produce significant disproportionality
Mixed systems combine district representation with list seats; whether outcomes become proportional depends on compensation rules.
Semi-Proportional and Alternative Approaches (Detailed)
Limited Vote (MMD)
Ballot: fewer votes than seats available
Translation effect
Gives minorities a better chance than block vote
Still not fully proportional
Cumulative Vote (MMD)
Ballot: multiple votes that can be stacked on one candidate
Translation effect
Allows cohesive minorities to concentrate support
Encourages candidate-centered campaigning
Single Non-Transferable Vote (SNTV)
Ballot: one vote in an MMD
Seat rule: top candidates win
Translation effect
Parties must manage nominations to avoid splitting votes
Key Design Choices and Their Representation Effects
District magnitude (M)
Low M (especially 1): tends toward majoritarian outcomes
High M: increases proportionality and small-party access
Electoral thresholds
Higher thresholds reduce fragmentation but exclude smaller parties
Interacts with M (effective threshold rises as M decreases)
Ballot type and voter behavior
Single choice: stronger strategic voting incentives
Ranking: can reduce spoilers; more expressive ballots
Preferential systems: can reward broad acceptability
Allocation formula impacts (in list PR)
D’Hondt: rewards larger parties slightly
Sainte-Laguë: more neutral for mid/smaller parties
Largest remainder: can benefit smaller parties depending on quotas/rounding
District boundaries
Compactness and community representation
Gerrymandering effects under SMD/FPTP
PR systems reduce boundary sensitivity but do not eliminate it
Level of seat allocation
National PR: high proportionality, weaker local ties
Regional PR: balances local ties with proportionality
Compensatory tiers: improve proportionality across regions
Evaluating Electoral Systems (Criteria)
Proportionality
How closely seat shares match vote shares
Accountability & clarity of responsibility
Single-party vs coalition governance
Ability to “throw the rascals out”
Representation
Geographic representation
Descriptive representation (e.g., gender, ethnicity) influenced by party strategies and lists
Party system effects
Incentives for coalition-building or polarization
Government stability and effectiveness
Majority governments vs coalition durability
Policy continuity vs responsiveness
Voter choice and expression
Candidate selection power (open lists, STV)
Preference expression (ranked ballots)
Simplicity, transparency, and trust
Counting and auditing complexity
Common Real-World Translation Patterns (High-Level)
FPTP/SMD plurality
Votes concentrate into seats for top party/parties
Smaller parties with dispersed support under-represented
List PR with moderate/high M
Seat shares track vote shares more closely
Multiparty parliaments and coalitions more common
Ranked SMD (AV/IRV)
Produces majority-supported winners per district
Legislative proportionality still limited by SMD structure
MMP
Overall results proportional (if compensation works fully)
Retains district MPs; coalition governments common
Parallel systems
Mixed outcomes; proportional tier softens but doesn’t correct majoritarian bias
Typical Trade-Off Summary
Majoritarian emphasis
Pros: decisiveness, clearer local link, simpler outcomes
Cons: disproportionality, wasted votes, minority under-representation
Proportional emphasis
Pros: fairness in seat-vote translation, broader representation
Cons: coalitions/fragmentation, sometimes weaker geographic accountability
Mixed approaches
Aim: combine local representation with proportional outcomes
Risk: complexity and design-dependent proportionality
Wondershare EdrawMind
