PV - Preferential Voting

With PV there are 120 Members of Parliament.

Each of the 120 electorates, including the Maori electorates, elects one MP. Voters rank the candidates – 1, 2, 3, etc – in the order they prefer them.

A candidate who gets more than half of all the first preference votes (that is votes marked “1”) wins.
If no candidate gets more than half the first preference votes, the candidate with the fewest number “1” votes is eliminated and their votes go to the candidates each voter ranked next.

This process is repeated until one candidate has more than half the votes. Large parties – and in particular the winning party – usually win a share of the seats in Parliament larger than their nationwide share of the first preference votes. It is hard for smaller parties to win seats in Parliament, but votes for smaller party candidates may influence who wins the seat because of second, third, etc preferences.

A government can usually be formed without the need for coalitions or agreements between parties.

PV in detail

With PV there would be 120 Members of Parliament.

Types of MPs?

There would be 120 electorates each electing one MP. On the basis of current census data there would be:

  • 27 South Island general electorates
  • 81 North Island general electorates
  • 12 Maori electorates

How would you vote?

Each voter has one vote to choose the MP they want to represent the electorate they live in, but this vote is transferable from one candidate to another in the order the voter prefers them. As a result, voters rank the candidates – 1, 2, 3, etc – in the order they prefer them.

Here is an example of a PV ballot paper:

How are MPs elected?

A candidate who gets more than half of all the first preference votes (that is votes marked "1") wins.
If no candidate gets more than half the first preference votes, the candidate with the fewest number “1” votes is eliminated and their votes go to the candidates each voter ranked next.

This process is repeated until one candidate has more than half the votes.

Here are simple examples of the three ways in which MPs can be elected.

  Example 1 Example 2 Example 3
Arawhata 10 10-10=0 10-10=0
Bailey 37 44+4=48 44+8=52 (elected)
Tawa 53 (elected) 46+6=52 (elected) 46+2=48

In Example 1, Tawa – with 53% of the votes – has more than half the first preferences and is elected on the first count.

In Example 2, Tawa (with 46 first preference votes) leads after the first count but does not have more than half the votes, so the lowest polling candidate (Arawhata) is eliminated. When Arawhata's votes are redistributed, Tawa gets six of Arawhata's 2nd preference votes for a total of 52 votes, enough to be elected with an absolute majority (that is, more than half the votes).

In Example 3, Tawa (with 46 first preference votes) leads after the first count but does not have more than half the votes, so the lowest polling candidate (Arawhata) is eliminated. When Arawhata's votes are redistributed, Bailey (with 44 first preference votes) gets eight of Arawhata's 2nd preference votes, enough to overtake Tawa and win the election with an absolute majority of 52 votes to Tawa's 48.

PV is used to elect the members of the House of Representatives in Australia, and in the 2010 election, just under 43% of MPs were elected on the first count (as in Example 1). Half of MPs led on the first count without an absolute majority but won after the distribution of preferences (as in Example 2). Slightly more than 7% of MPs did not lead on the first count but won a majority after the distribution of preferences (as in Example 3).

What would Parliament look like?

PV usually leads to significant differences between voters’ first preference support for political parties and the makeup of Parliament.

This is because in each electorate race there is only one seat and therefore only one winner, and elections are decided by the number of electorates each party wins, not the total number of votes they receive across the country.
Large parties – and in particular the winning party – usually win a share of the seats in Parliament larger than their nationwide share of the first preference votes.

Although it is hard for smaller parties to win seats in Parliament, votes for smaller party candidates may influence who wins the seat because of second, third, etc preferences.

These features of PV can be illustrated by looking at the results of the last two elections for the 150-member House of Representatives in Australia.
pv1.png
In 2007 the Labor Party won 43% of the first preference votes and got 55% of the seats in the House of Representatives. In the same election, the Greens won nearly 8% of first preference votes and no seats.

In the 2010 Australian parliamentary elections, Labor won 38% of first preference votes and got 48% of the seats in the House of Representatives, while the Liberal-Nationals won nearly 44% of the first preference votes and 48.7% of the seats. The Green Party won just under 12% of the first preference votes but less than 1% of the seats. However, the preferences of Green Party voters influenced the overall result of the election, because nearly 80% of them went to Labor candidates.
pv2.png
What type of government is usually formed?

Because it is difficult for small parties to be elected under PV, majority governments are most common. The 2007 election results in Australia are a good example of this, but the 2010 Australian House of Representatives elections show that majority governments will not always result from PV. A minority Labor government was formed, supported by the Green MP and three Independents.

Where is PV used?

PV is used for elections to the House of Representatives in Australia, as well as for elections to the lower houses in five of the six Australian state Parliaments. PV is also used for parliamentary elections in Papua-New Guinea.
What are other names for Preferential Voting (PV)?

In many parts of the world (including the United Kingdom), PV is called Alternative Voting (or AV). In the United States, PV is usually referred to as Instant Run-off Voting (IRV). Political scientists have classified PV as a single-member majoritarian system.

 

Last updated: 20 October 2015