Explanation: A North Island electorate will disappear before the next election; here’s why

In the South Island, the number of electoral seats is always fixed, by law, at 16, while the number of electoral seats in the North Island depends on the size of the population as recorded in the census.

The North Island will lose an electorate seat because the population of the South Island grew faster than the population of the North Island.

The general electoral population of the North Island is 3,353,982, 5.5% more than the last census of 2018. For the South Island it is 1,120,593, 7% more than 2018 .

how does it work

The law requires that every electorate in the country be the same size. This is achieved through a two-step process.

The first step, announced yesterday, is to determine the number of electorates and the ideal size of the electorate. The second step is to adjust the boundaries to try to get all voters within 5% of the ideal size.

The process begins in the South Island.

Officials calculate the size of the target electorate by taking the electoral population of the South Island (1,120,593) and dividing it by 16 (the legislated number of seats) to get each electorate’s “quota” or size in the South Island.

The current quota for each seat in the South Island is 70,037.

Officials then take the North Island’s electoral population (3,353,982) and divide it by the South Island’s share (70,037) to determine the number of electorates there will be in the North Island (48, below 49 during the last two elections).

Electoral population of the North Island (3,353,982) ÷ share of the South Island (70,037) = 48

The share of general electorates for the North Island is 69,875 people (3,353,982 ÷ 48) and differs from the figure for the South Island because there must be a round number of electorates.

An electorate in the North Island will be removed and the boundaries of the remaining electorates will be moved, so that the general electoral population of each electorate will fall between 66,381 and 73,369.

The number of Māori electorates will remain at seven. For Māori voters, the quota is 74,367 people.

One of the Māori electorates, Ikaroa-Rāwhiti, will also have its boundaries redrawn because its electoral population is currently outside the 5% tolerance.

Given that New Zealand has 120 parliamentary seats (excluding the flyover), this means that there will now be one more seat on the list.

In total, there will be 71 electorate seats and 49 list seats.

Julia Gabel is a political journalist based in Wellington. He joined the Herald in 2020 and has recently focused on data journalism.