World Election Forecast

Polling averages and predictions for elections worldwide

Types of Proportional Representation

Out of all potential replacements for the existing FPTP (First Past the Post) system, Proportional Representation by far the most widely suggested. Used in more than half of countries worldwide, it has been advocated by many groups as a replacement for the existing system on the basis of its ability to accurately represent the wishes of the entire electorate.

There are several different types of Proportional Representation, with varying levels of proportionality, vote thresholds, and regional representation. These are: Mixed-Member Proportional, Party-List Proportional, Open List Proportional and Single Transferable Vote (which is sometimes counted separately). Using the 2015 UK parliamentary elections as an example, we can analyze the several main types of proportional representation used today.

Mixed-Member Proportional (Germany)

Mixed-Member Proportional (MMP) is a two-tiered voting system which takes into account both local results and national results to allocate seats. Electors select both a local candidate for the constituency, and select members of a national party, which determines the overall composition of the legislature.

Total Vote =  Constituency Seats Won + Party List Vote (distributed according to how many seats left until proportionality, and subject to the cutoff)

In Germany, a 5% threshold is enacted meaning that a party must gain over 5% of the vote in order to be counted in the Party List Vote. This threshold is down to 3% if a party gains over 3 direct constituency seats. It is only after constituency seats are awarded that the party list is used to calculate how many additional seats are given to each party to ensure proportionality.

Usually, half of the total seats are constituency seats. Thus, we assume that the UK has 325 constituency seats and 325 additional seats.

Example: UK 2015 election with German MMP

UK-PR-GER

  • Smaller regional parties (Plaid Cymru, Sinn Fein, DUP, and the SDLP) are only in parliament because of their ability to gain regional seats.
  • Larger regional parties (only the SNP) have gained over 3 direct constituency seats, and thus are able to gain additional seats in proportion to their total national vote, despite being under the 5% cutoff.
  • The large parties (Conservatives, Labor, UKIP and Liberal Democrats) are above the 5% cutoff, meaning they gain votes in proportion to their popular vote.
  • A noticeable absence is the Green party. We assume they fail to win in their new, enlarged constituency, and as their popular vote falls below 5% they do not gain representation.

In other World Election Forecast simulations, such as the Five Parties of America and Electoral Reform in British Columbia, we use MMP.

Party-List Proportional (Israel)

Party-List Proportional, or just PR, is a much simpler voting system which takes into account just national results to allocate seats. Electors select a single national party, which determines the overall composition of the legislature. Israel uses a closed-list system, where voters only vote for parties and do not determine the order of the election of candidates. A 3.25% threshold is enacted for parties wishing to enter the legislature.

Example: UK 2015 election with Israeli PR

UK-PR-ISR.png

  • Smaller regional parties (Plaid Cymru, Sinn Fein, DUP, and the SDLP) are unable to gain representation, as they fall below the 3.25% cutoff
  • The large parties (Conservatives, Labor, UKIP, Liberal Democrats, SNP and the Green Party) are above the 5% cutoff, meaning they gain votes in proportion to their popular vote.

Open Party-List Proportional (Brazil)

Similar to above, Open Party-List Proportional, or just PR, is a much simpler voting system which takes into account just national results to allocate seats. Electors select a single national party, which determines the overall composition of the legislature. However, voters can also vote for individual candidates within a party, determining the order of selection of candidates. In Brazil, there is no threshold for entering the legislature – any party can enter should it muster sufficient votes.

Example: UK 2015 election with Brazilian PR

UK-PR-BR

  • Parties with a share of the votes as small as the Alliance Party (0.2% of all votes) can gain access to the legislature.
  • The D’hondt method of calculating votes favors larger parties – if the Webster/Sainte-Laguë method is used instead, two smaller parties (the National Health Action Party and the Trade Unionist and Socialist Coalition) gain representation. This has a fragmentary effect on politics – note how in Brazil, parties rarely gain above 20% of the votes

Single Transferable Vote (Northern Ireland)

Under STV, the United Kingdom would be grouped into multi-member districts, with each voter ranking the candidates in the district in order of preference. The candidates which reached a certain amount of support would win a seat in the riding, and have his/her votes redistributed to other candidates. This form of voting is not always counted in Proportional Representation, however, it often produces quite similar results, but with parties closer to the political center tending to dominate.

The UK is divided into 12 regions: East, East Midlands, London, North East, North West, Northern Ireland, Scotland, South East, South West, Wales, West Midlands and Yorkshire and The Humber

Example: UK 2015 election with Northern Irish STV

UK-STV

  • Similar to the example of Brazil, parties with a share of the votes as small as the Alliance Party (0.2% of all votes) can gain access to the legislature.
  • The distribution of results is largely proportional to the share of the popular vote; however, minor parties benefit slightly more from the redistribution.
  • The calculation for results is an inexact art, which requires estimates on the redistribution of votes. See the Appendix at the bottom of this post to view the assumptions made.

Additional Links

Analysis of the UK under the Alternative Vote system (2015)

Analysis of the UK under the Alternative Vote system (2010)

Analysis of the UK under the Alternative Vote system (Summary)

Analysis of the Canada under a PR system (2015)

Analysis of the US under a PR system (2015)

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