How people elect parliaments
New Zealand has a unicameral Parliament of which the sole house is the House of Representatives, a composite assembly of at least 120 members.
From its establishment in the 19th century the New Zealand House of Representatives had been elected by plurality voting in single member divisions. However from 1996 the mixed-member proportional system for electing a composite assembly was adopted.
At elections the voters cast two separate ballots, one for candidates nominated in 70 local single member divisions (termed ‘constituencies’) and a separate ballot for political parties, the latter being used to allocate a further 50 seats on the basis of the parties’ national vote totals.
The 70 local divisions are divided into ordinary constituencies and Maori constituencies. Individual voters of Maori ethnicity are entitled to enrol to vote in either form of constituency, but not both, and must register their choice between the two forms of voting in advance of the elections. The number of seats (out of 70) allocated to the Maori voting pool – currently 7 – is determined by the proportion of total voters which register as Maori seat voters. A set of boundaries for the Maori constituencies are determined separate from (and overlaying) the boundaries of the ordinary constituencies.
Members for all the 70 single member divisions are directly elected by the plurality voting method.
A further number of at least 50 members are allocated to parties by the open party list system of seat allocation, using the Sainte-Laguë formula, in the numbers required such that the party composition of the whole assembly is ‘levelled‘, or made party-proportional overall. The national party vote totals are used to calculate a proportional share of a nominal total of 120 seats for each party which wins more that 5% of the national vote. If a party has won more local constituencies than it is entitled to according to the national calculation, such ‘overhang’ seats are nevertheless awarded to the elected local member and the total size of the House is increased accordingly (for example, the 2014 election resulted in a House of 121 members).
Terms are up to three years.
New Zealand has the representative parliamentary system of government, in which nominal executive authority is vested in the Queen and exercised by a Governor-General appointed by her. However, actual executive power is exercised by the Prime Minister on the basis of the continuing confidence of a majority in the House of Representatives.
[Inequality in the effective influence of voters caused by variations in xxx division enrolments]
[nomination openness – party configurations]
[summary of results]
[Inequality in the effective influence of voters caused by variations in division turnouts (formal votes)]
[inequality by margins]
1996 – 1999 – 2002 – 2005 – 2008 – 2011 – 2014 – 2017
[data source – data completeness – anomalous contests]
[Datasets are not yet published]