Oz Blog News Commentary

NZ 2020 – the seats and the swings

October 22, 2020 - 09:30 -- Admin

The New Zealand electoral system tends to produce a flattening effect on the results. Most electorate results don’t really make a difference to the national outcome so the results analysis tends to just look at the national figures. But there is value in delving down and looking at the geography.

Overall the swings away from National and towards Labour were remarkably consistent. In this post I’ll include some maps and tables showing the swings in different parts of New Zealand, and look at how the swing on the candidate vote tended to be bigger in National seats.

I have compiled an estimate of the 2017 results based on the 2020 redistribution. I don’t believe anyone else has done this in New Zealand. This means it is possible to calculate swings from this data. You can view these 2017 estimates here. Elections NZ did not make it easy to grab all the booth data in one go – the data was in 142 separate CSVs in a messy format, there are no unique booth IDs and the macrons used for many electorate names and booth names were treated inconsistently by my software. But it’s finally finished and will be used in this post.

Firstly, let’s look at the electorate seats. I’m basing this analysis on data I downloaded on Tuesday evening.

Prior to the election, National held 42 seats (including one newly created notional seat), Labour held 29 and ACT held one.

Following this election National has been reduced to just 26 seats, with Labour on 43 seats, with ACT, Green and the Māori Party each holding one seat. Interestingly this means that every party in Parliament holds at least one electorate seat.

Labour gained fifteen seats off National, Green gained one seat off National, and the Māori Party regained Waiariki from Labour. Most of these changes were in regional seats. National lost four seats in Auckland and one each in Wellington and Christchurch, with the other ten in regional areas.

This map shows the winner of each general seat, with the seats that changed in brighter colours.

You can click through to see the candidate vote and swing for the four biggest parties, as well as the change in margin, for each electorate.

But the votes that really matter are for the party vote, which decides the share of seats for each party in parliament.

The next map shows Labour’s party vote swing per general electorate, and can be toggled to show the swing for National and Green. It’s zoomed in on Auckland but you can scroll around or zoom out.

Labour tended to get smaller swings in the core of the Auckland area, and did much better on the outskirts of Auckland and in regional areas. You can see a similar trend in the seats surrounding Christchurch.

Another way to look at this is to break the country up into regions. I broke up seats into Auckland, Christchurch, Wellington and the remainders of the North and South islands, as well as the Maori seats. This table shows the swings to or from the six parties with representation in the new or old parliaments in each region.





North Island

South Island


New Zealand

The race in the Maori electorates is very different to the rest of the country, with a very high Labour vote and a very low National vote, so the swings were much less dramatic.

The boost in the Green vote mostly took place in the big cities, while Labour’s biggest gains took place in the regional seats.

Another way to break down the results is to look at how much the candidate vote swung in Labour and National electorates. The swing to Labour in seats they retained averaged 11.5%, while the swing to Labour in seats they gained averaged 23.8%. The swing against National in seats they retained averaged 21.5%. This suggests that the biggest movement, at least on the candidate vote, took place in National electorates.

Of course there is a difference between how people vote on the party vote and on the candidate vote. There was a slightly higher Labour vote on the party vote (49.1% as against 47.5%) while the National vote was much higher on the candidate vote (35.7% as against 26.8%).

There is a history of these sorts of gaps appearing in past elections, which often result in one party winning almost every seat on the party vote while their opposition performs more respectively on the candidate vote, but that’s a story for another day.