Proportionality

Does the voting system translate votes into seats so that a party's share of seats reflects its share of votes?

Proportionality is widely considered to be one of the major criteria for assessing electoral systems. As the editors of The International IDEA Handbook of Electoral System Design note, "a parliament should be functionally representative of the party-political situation that exists within the country."

The editors add: "Through the representation not only of political parties but also of independent MPs, an effective parliament should adequately reflect the ideological divisions within society."

Similarly, the Report of the Royal Commission on the Electoral System in New Zealand states, "When they vote at elections, voters are primarily choosing between alternative party Governments. In the interests of fairness and equality, therefore, the number of seats gained by a political party should be proportional to the number of voters who support that party."

It is important to note that proportionality involves a trade-off. The greater the weight given to the need to value all votes equally (and the consequent representation of both big and small parties in Parliament), the less likely it will be that one party will have enough seats in Parliament to form a government on its own.

Each of the voting systems tends to perform on the question of proportionality in the following ways:

  • MMP

    MMP is a proportional representation voting system. A party's share of all the seats in Parliament closely mirrors its share of the total votes as long as the party crosses one of two legal thresholds. Larger parties as well as smaller parties (those with either 5% of the party vote or at least one Electorate MP) are entitled to a share of all the seats in Parliament that closely reflects their share of the party votes.

    More parties are elected to Parliament, and this allows for a greater range of political views to be expressed. Independent MPs cannot be elected via the party vote. However, it is possible – but most uncommon – for an independent candidate to be elected as an Electorate MP.

     

  • FPP

    A party's share of seats does not usually mirror its share of votes throughout the country as a whole.

    Larger parties – and particularly the winning party – usually win a share of the seats in Parliament larger than their share of all the votes across the country.

    Smaller parties usually receive a smaller share of seats than their share of all the votes, unless their support is concentrated in a few electorates. The winning party often receives a majority of seats with less than a majority of all the votes.

    Sometimes the party with the most votes overall does not win the most seats. MPs mainly come from two larger parties with the likelihood that a somewhat narrower range of political views is expressed in Parliament. It is possible – but most uncommon – for an independent candidate to be elected as an Electorate MP.

     

  • PV

    A party's share of seats does not usually mirror its share of first-preference votes throughout the country as a whole.

    Larger parties – and particularly the winning party – usually win a share of the seats in Parliament larger than their nationwide share of the first preference votes. Smaller parties usually receive a smaller share of seats than their share of all the first preference votes, unless their support is concentrated in a few electorates, but votes for smaller party candidates may influence who wins the seat because of second, third, etc preferences.

    The winning party often receives a majority of seats with less than a majority of all the first preference votes. Sometimes the party with the most first preference votes overall does not win the most seats. MPs mainly come from two larger parties with the likelihood that a somewhat narrower range of political views is expressed in Parliament.

    It is possible – but very difficult – for an independent candidate to be elected as an Electorate MP.

     

  • STV

    STV is a form of proportional representation. The number of MPs elected from each political party roughly mirrors the party's share of all the first preference votes across the country. It allows smaller parties and independent candidates with local support to be elected to Parliament.

    This becomes more likely as the number of MPs elected from any one electorate increases. STV tends to see more parties elected to Parliament, and this allows for a greater range of political views to be expressed.

     

  • SM

    Under SM there is an element of proportionality – in the supplementary seats, but normally the overall result is not proportional (that is, it does not closely mirror the party vote). SM would likely over-represent larger parties in Parliament and under-represent smaller ones.

    This is because three-quarters of the seats in Parliament are elected by FPP and because the party vote determines a party's share of the 30 list seats only.

    Smaller parties with a minimum degree of support will qualify for a share of the 30 supplementary list seats, which will allow for a somewhat wider range of views to be expressed in Parliament. Independent MPs cannot be elected via the party vote. However, it is possible – but most uncommon – for an independent candidate to be elected as an Electorate MP.

     

 

Last updated: 29 January 2013