Donate to help Dr. Dahl the dodo and his team strengthen US democracy!

Proportional Representation 101

Proportional representation is a system in which seats in an elected body are awarded in proportion to the overall preferences of the voters.

Introducing PR

A multi-winner system

Proportionality depends on district magnitude

Political parties are central

Constituencies are larger

Mixing PR with other systems

PR Around the World

Why Use Proportional Representation?

Italian 2018 Chamber of Deputies absentee Open list PR ballot (voting from abroad) showing the 8 political parties fielding candidates. Voters vote by making a mark on the rectangle containing their preferred party and may write the name of a party's candidate inside the rectangle if they disagree with the order of the party list. (Wikimedia Commons)

In many American elections, one representative is elected in each separate geographic district by the people who live there. These kinds of elections are "winner-take-all": The candidate with the most votes in a district wins all of the representation for that area.

By contrast, in Proportional Representation (PR) legislative seats are awarded in proportion to the total votes cast for each political party (e.g., 30% of the vote yields roughly 30% of seats).

Introducing PR

District magnitude: The technical term for the number of winners elected in a single election contest.

A multi-winner system

Unlike plurality or majoritarian systems, PR only happens in multi-winner contexts (since you can't elect one representative proportionally!). PR cannot be used to elect the president or a governor.

Multi-winner PR contests may occur at large across a country, state, or city. Or they may be in multiple (multi-winner) districts.

Proportionality depends on district magnitude

Despite its name, PR is not inherently proportional. Its proportionality depends on the district magnitude in each contest. The more winners in each contest, the more proportional outcomes can be.

This is because the threshold for winning reduces with every increase in district magnitude. In a two-winner district, a candidate must win more than a third (33%) of the vote to win (depending on the allocation formula used); in a three-winner district, the threshold is a quarter (25%); and in a four-winner district, a fifth (20%). And so on.

In a 2-winner contest, outcomes cannot be very proportional unless there happen to be two candidates that both win about 50% of the vote each.

With a district magnitude of 7, outcomes can become more proportional. Political parties that receive more than 12.5% of the vote are likely to win a seat, though some parties will be overrepresented and others underrepresented (or not represented at all).

When district magnitude reaches 100, political parties that receive just 1% of the vote will win election (if there's no other threshold for election).

Party lists: official lists of candidates nominated by each political party. These lists indicate who, and in what order, the political party wants its candidates elected.

Party lists on public display at a Rome, Italy, polling station (March 2018 election) (Wikimedia Commons)

Italian 2018 election absentee Open list PR voting from abroad materials showing the Chamber of Deputies ballot paper (1) and party lists (7). (Wikimedia Commons)

Political parties are central

Party lists lie at the core of PR systems. Seats are awarded using the lists based on the percentage of votes the party receives, with the candidate at the top of the list being elected first (and those at the bottom last or not at all).

In Closed Party List PR, voters do not have any Election Day influence on which candidates are elected. The voter may only indicate which party they wish to vote for. The party list does the rest.
In Open Party List PR, voters have some degree of influence over the order in which candidates are elected. In many systems, voters can select or rank candidates of a particular party, thereby influencing the order in which they are elected.

In Indonesia, which uses a very candidate-oriented form of Open Party List PR, voters select one candidate from within the party lists and a party's seats are allocated to the candidates in order of how popular they were.

Italy uses a more party oriented open list, where voters by default vote for the party list but may write in the name of a candidate to indicate they want that candidate elected before others on the list.

Independent or unaffiliated candidates generally can run for office, at least in Open Party List PR, though they may be at a disadvantage due to the party representation logic of PR systems.

Party lists on public display in an Albanian polling station (May 2025 election): OSCE Parliamentary Assembly (Flickr)

Open Party List PR ballot (truncated) from the 2019 Indonesian House of Representatives election showing candidate lists of the first 12 (of 20) political parties contesting the seven-seat Jakarta II district. Voters vote by selecting a candidate from within one of those lists. Their vote counts for the party and the candidate. (William and Mary Law School)

Closed Party List PR ballot from the 1993 Cambodian election showing the 20 political parties contesting the election. Voters select a party and do not have any say over the order in which party candidates are elected. (Wikimedia Commons)

Constituencies are larger

As Santucci and Ketcham explain, PR's "main function is to permit parties ... to aggregate their votes over larger areas than is possible under single-seat or otherwise small districts."

Multi-winner districts tend to be more populous than single-winner districts and each constituent has multiple elected representatives. Citizens can choose which of the elected representatives from their district they consider theirs. Partisan affiliation — and the ideologies and identities that ground it — are likely to be the most important links between representatives and those represented by them.

As discussed below, the placement of district lines is less important in PR (and non-existent in at-large PR), meaning the system can help mitigate or avoid partisan contests over redistricting and reduce the effectiveness of gerrymandering.

Mixing PR with other systems

PR is frequently mixed with other electoral systems.

This is because PR tends to shift focus from local candidate-constituency relationships to national party platforms. If a polity values proportional outcomes AND the representation of local interests and identities, they will likely mix PR with a single-winner district system.

The most common mixed systems are:

Mixed Member Proportional (MMP): A mixed single-winner and multi-winner proportional system in which every voter has two votes:

For a local candidate in a single-winner district, typically using first-past-the-post to select the winner.
For the candidate's party in a national at-large electorate, using PR.

MMP is proportional. The number of district seats relative to the number of party-list proportional seats varies, but MMP always includes formulae, top-up seats, or other adjustments to ensure overall proportionality of party votes to seats in the legislature.

Mixed Member Majoritarian (MMM): A mixed system in which seats in a legislative body are elected using two different logics. Typically, one set of seats in the legislature are elected using PR and others using a majority or plurality logic (using, for example, first-past-the-post, Plurality Block Vote, or Majority Runoff). Voters may get two votes, one for each class of seats, or the proportional seats may be allocated based on the party preference revealed in the majority or plurality contest.

The number of proportional seats relative to plurality or majority seats varies, but MMM does not include mechanisms to ensure overall proportionality of party votes to seats in the legislature. This means overall results are not proportional.

An MMP ballot from the 2011 New Zealand election showing the party (proportional) and candidate (first-past-the-post) columns that voters use to express their preferences. Unlike List PR, voters may vote for (a candidate from) a different political party in their local district than the party they vote for with their party vote (Wikimedia Commons)

There are a lot of technical terms on this page! Check out the glossary for definitions.

Glossary

PR Around the World

PR is common around the world, with around 110 countries using it for at least some seats in their national lower house, including Germany, New Zealand, and South Africa. Around 70 use a closed party list and ~45 countries use an open party list.

About 65 countries use PR on its own. Another 15 use PR for almost all seats (employing single-winner districts using First-past-the-post only in a few less populated areas or for overseas voters). The rest mix PR with another system. Four countries (Bolivia, Germany, Lesotho, and New Zealand) use Mixed-Member Proportional and almost 30 countries (including Japan, Lithuania, Mexico, and Taiwan) use versions of Mixed-Member Majoritarian.

Almost 60 countries around the world have a national (at-large) PR constituency, including Israel, the Netherlands, Russia, and South Africa. The district magnitudes in the ~17 countries electing all their lower house legislative seats in one national constituency ranges from 31 (in Greenland) to 450 in Ukraine, with an average district magnitude of 130. In PR countries without a national PR constituency, by contrast, district magnitudes range from 1 to 71 (in Iraq), with most countries having no districts electing more than 20 winners.

Want to know more?

Electoral Systems of the World

Why Use Proportional Representation?

Arguments for PR

(Click to expand)

Better translates votes for parties into seats won in the legislature

PR more accurately translates votes into seats than existing US electoral systems. PR can avoid "wrong winner" outcomes, in which a party that gets a majority of votes does not win a majority of seats. It also "wastes" fewer votes, meaning fewer situations in which a majority of voters cast their ballots for someone other than the winning candidate or party.

Creates more choice

As long as the district magnitude is sufficiently high, PR encourages the formation and election of multiple political parties. In districts electing 9 or more representatives, political parties need only win 10% of the vote to gain representation. New political parties should form, fewer seats should be uncontested, and voters should have more viable choices.

Improves representation

More political parties running and winning translates to better representation of the full diversity of Americans' opinions, identities, and interests than existing two-party politics. More voters will be represented by at least one representative that they identify with.

Makes gerrymandering is less effective

Under PR, it would be harder to engineer particular outcomes using district lines. The exact placement of district lines is less important in PR than in single-winner systems, because there are:

Fewer districts to draw and more people per districts: Meaning less scope to engineer outcomes (or crack and pack voters into particular districts).
More than one winner in each district: Making it less rewarding to engineer particular outcomes for a particular party or group.

The greater the district magnitude, the less rewarding gerrymandering becomes.

Encourages coalition governance

When district magnitude is high, PR rarely results in single party majorities. Coalition governance (the sharing of power between multiple political parties) may become the norm, encouraging interparty negotiation and compromise.

Arguments Against PR

(Click to expand)

Encourages coalition governance

When district magnitude is high, PR rarely results in single party majorities. Coalition governance (the sharing of power between multiple political parties) may become the norm, which can result in:

Unstable majority coalitions, in which membership and leadership frequently changes or is structured around bills currently on the floor.
Legislative gridlock if coalition parties do not have significant overlap in their policies or support base.
Disproportionate power of small political parties because large parties are forced to make concessions to maintain the coalition and preserve their majority status.

Districts are larger

If single-winner districts are reformed to Party List PR without also increasing the number of legislators in the body, the new multi-winner districts will be more populous (district magnitude times more populous) than the single-winner districts they replaced. In the context of the U.S. Congress, where there is an average of more than 750,000 people per district, this makes for some very large and populous districts (at minimum 2 million). For this reason, expanding the size of the legislature is often a part of PR reform packages.

Encourages party discipline

Party List PR shifts the focus of representation from local candidate-district relationship to national party platforms. Governance is carried out by political parties, not individual legislators, especially in Closed List systems. Parties negotiate deals with other parties. Party List PR encourages representatives to represent their party supporters, not their district as a whole, and vote the party platform in the legislature (even when it is not in their district's broader interests or when a majority of voters in the district oppose the policy).

Provides a platform for extremist parties

Because Party List PR allows for the representation of a greater diversity of voices, extremist parties may gain a voice in the legislature in a way that other electoral systems will not allow.

Effect of PR

What we know

With district magnitude, more political parties.

As district magnitude increases in a PR system, so does the expected number of political parties that win legislative seats (Shugart and Taagepera, 2017). Multi-party systems are less likely in List PR with 3- or 5-winner districts than PR with district magnitudes of fifty.

Additionally, in the U.S. context, it should be noted that US political institutions (primary elections, the U.S. Senate, the Electoral College) inhibit the creation of multiple political parties and, at the federal election, limit district magnitude (since seats in the U.S. House are apportioned to states, with a median of 6 Representatives in a state). For more see: Santucci, Shugart, and Latner, 2023.

Finally, there are issues with causation. Historically, PR has been adopted after multiparty competition emerges. As Josep Colomer famously explained, “It’s Parties That Choose Electoral Systems” not the other way around (Colomer 2005; Boix 1999).

With district magnitude, more proportionality of party votes-to-seats outcomes.

Moving from plurality or majority systems to PR results in a closer translation of the aggregate vote for a particular party to the number of seats it wins (in a geographic unit), with more proportional results with higher district magnitudes (Anckar 1997; Gallagher, 1999).

With Closed Lists, party governance.

Closed Party List PR typically coexists with strong, disciplined parties (as opposed to weak or loosely disciplined parties). Governing is done by and between these strong, disciplined parties (Gerring, Thacker, and Moreno, 2005).

In presidential systems, potentially unstable coalitions.

A legislature with more political parties poses challenges in presidential systems, like the U.S., where executive and legislative are strictly separate, and competing, sources of power. Instead of a stable coalition of parties, in presidential systems with PR legislative business may be punctuated by diverse and changing sets of party coalitions mobilized around the business of the day. This has been characterized as chaotic and undesireable by some scholars (e.g. Linz, 1990).

More women elected

There's a consensus that List PR systems are associated with the election of more women, for at least two reasons. First, in the centralized nomination processes associated with party list creation, political parties nominate a higher proportion of female candidates to their lists. Second, because voters evaluate candidates as a slate or list, rather than as individuals, they are more likely to "balance their ticket" (Krook, 2016; Brandenburg and Lühiste, 2026).

What we don't know

How PR actually works in the US

It hasn't been tried, so we have no empirical evidence on how List PR plays out in the U.S. The US experience is unlikely to be identical to the closest analogs in Europe (where presidential systems are are rare) or Latin America (with different political cultures).

Reading List

Theoretical Grounding

Josep Colomer (2005) “It's Parties that Choose Electoral Systems (Or, Duverger's Laws Upside Down).”
Matthew S. Shugart and Rein Taagepera (2017) Votes from Seats: Logical Models of Electoral Systems.

Overview

Marek M. Kaminski (2026) Proportional Representation Primer.
Peter Buisseret and Carlo Prato (2025) Proportional Representation (Democracy Reform Primer Series).