New Zealand will go to the polls next year at their next general election, and the electoral map of New Zealand has been redrawn in advance of that election.
New Zealand’s parliament is elected via mixed member proportional, with a majority of MPs elected to represent single-member electorates using first-past-the-post, and the remainder elected from party lists as top-ups to ensure overall proportionality.
This means that, most of the time, the specific seat results don’t matter to the national result, although they matter to the individual candidates and can shape the make-up of a party’s caucus. The only exceptions are where a party wins more electorates than their share of lists (in the case of Te Pāti Māori) or where a party would fall below the 5% threshold to win list seats, but qualifies due to holding an electorate.
Still, it is interesting to look at how the boundaries have changed and to attempt to estimate the margins in each new electorate. I have partly been prompted to do this to help with some work I am doing for my part-time employer, software company GovConnex.
The draft boundaries were released early in 2025, with the final boundaries released in August.
As part of this work, I have added the full New Zealand 2023 dataset to my data repository. My repo now contains full results for six New Zealand elections, all the way back to 2008. The 2023 dataset is free for all but the others can be accessed if you sign up as a Patreon donor for $8 (+GST) per month.
So firstly, the big changes.
New Zealand’s South Island is mandated exactly 16 electorates. The ratio of residents to seats on the South Island is then used to calculate how many North Island electorates and how many Māori electorates should be created. Since this process was introduced in the 1990s, the other two categories have always grown faster than the South Island. From 1996 until 2020, the number of North Island seats grew from 44 to 49, and the number of Māori electorates grew from five to seven. But this year, there was a reversal, with the North Island losing one seat (although the Māori roll came close to qualifying for an eighth seat).
So the total number of electorates shrunk from 72 to 71, and the (minimum) number of list seats increased from 48 to 49.
To use my Australian federal redistribution parlance, this meant that the North Island underwent a major redistribution while the South Island and the Māori electorates underwent minor redistributions. And this can be seen in the changes.
Just seven of sixteen South Island electorates had changes, and most of them were relatively minor. Just two of the Māori electorates had a change. But all but seven North Island electorates were redrawn.
Eight North Island electorates were given a new name, not counting the changes in the northern Wellington area.
In the northern suburbs of Wellington, three electorates were redrawn into two, with totally new names. Mana, Ōhāriu and Ōtaki were replaced by Kenepuru and Kapiti. It was quite hard to judge which of those three seats was abolished, but I have landed on Ōhāriu, as the two new seats each contain slightly more of the other two old seats.
Changes on the North Island were most significant around the two biggest cities. Every seat in the Auckland area underwent changes, even if there was no abolitions. The seats in the outer west underwent the biggest changes. New names reflect the significant redrawing: Henderson replaces Te Atatū, Glendene replaces Kelston, and Waitākere replaces New Lynn. Changes were less dramatic in the south-west of the Auckland area, but Panmure-Ōtāhuhu moved south and was renamed Ōtāhuhu.
Changes in the centre of the island were minimal: Port Waikato, Waikato, Hamilton East, Hamilton West, Coromandel and Taupō were left untouched. East Coast was renamed East Cape but with no changes. The changes to Taranaki-King Country and New Plymouth were miniscule.
There was some significant changes to Tauranga and Bay of Plenty, with minor knock-on effects on Rotorua. This led to Bay of Plenty being renamed Mt Maunganui.
Changes begin to ramp up as you approach Wellington. In addition to the major redrawing of the northern suburbs, the two inner city electorates of Wellington Central and Rongotai were renamed Wellington North and Wellington Bays respectively.
Most of the changes on the South Island were limited to the Christchurch area. Christchurch East and Ilam both grew into Christchurch Central, which then pushed into Wigram, and Wigram then pushed into Selwyn. There was also a change to the Southland-Invercargill border.
In the Māori electorates, the southern electorate of Te Tai Tonga, which covers the entire South Island and most of the Wellington area, lost the remainder of Lower Hutt to Ikaroa-Rāwhiti. The other five seats were untouched.
Overall, 9.3% of voters were moved to a new electorate.
As for the partisan changes, you can see my estimates of the first-placed and second-placed candidate and party votes in each electorate in this spreadsheet.
I had a dilemma in how I dealt with the electorate of Port Waikato. That seat’s election was delayed due to the death of a candidate, and thus was held as a by-election (incidentally adding one extra National Party seat to their total). Labour did not contest the by-election and the National margin was vastly larger than it would have been if the election had been held alongside every other contest. Voters in Port Waikato did cast a party vote on the day, so I have used that to calculate the margin. In the end there were no changes to that seat’s boundary so it affects no other electorates.
There were four partisan changes:
- The National seat of New Lynn was renamed Waitākere and became a notional Labour seat, with the margin flipping from 2.5% NAT to 0.9% LAB
- The Labour seat of Te Atatū was renamed Henderson and became a notional National seat, with the margin flipping from 0.4% LAB to 2.4% NAT
- The Green seat of Wellington Central was renamed Wellington North and became a notional Labour seat, with the margin flipping from 13.4% GRN to 0.5% LAB.
- The Labour seat of Wigram became a notional National seat, with the margin flipping from 3.2% LAB to 7.2% NAT
In addition the Labour seat of Ōhāriu was abolished.
So this produced a net gain of one National seat, a net loss of one Labour seat, and a net loss of one Green seat. The total electorate seats thus became 45 National, 16 Labour, 6 Te Pāti Māori, 2 Green and 2 ACT. But of course this wouldn’t change the total seat allocation due to the list seats adjusting accordingly.
So that’s it for this topic. I will probably not be analysing the NZ election in depth, but since I was calculating this data I thought I would pull it together for a blog post. I hope to do podcasts around election time.
I also recommend reading Rustie at the Overhang, who published two posts earlier this year looking at the redistribution process and numbers.
Finally, I have included a map showing the general electorate boundaries for 2020-23 and 2026-29. You can toggle off the boundaries and labels for each cycle. If the labels look out of place, toggle that layer on and off and they should recentre.
New Zealand economy is in serious trouble and looks like it will tip into another recession. It will be interesting to see if the incumbent government can get another term and turn it around like federal Labor did here. I do find their whole electoral system fascinating.