Our electoral system has long recognised that the counting process must allow for errors. Under first past the post (FPP), electorate-level recounts are an effective solution.
An error of a few hundred votes in an electorate with a margin of a few thousand does not matter under FPP and will not have any impact on the make-up of parliament.
But under MMP, no matter how big the candidate vote margin is, a relatively small error in the party vote could affect who gets into parliament.
MMP has a mathematical problem. In a mathematically perfect world, the next parliament would be made up of the following number of MPs: National, 48.4; Labour, 34.2; Green, 14.8; Act, 11; NZ First, 7.7; and Te Pāti Māori, 5.9. Only Act is going to be happy with this and no one is going to volunteer to be 0.4, 0.2, 0.8, 0.7 or 0.9 of an MP.
Since fractional MPs are not an option, New Zealand, and many other MMP jurisdictions, use the Sainte-Lague formula to allocate seats in parliament. It is essentially a method of rounding so that parliament can be made up of a whole number of MPs for each party.
Most of the time a small change in party votes won’t impact the allocation of seats. In this election, NZ First is closest to a seat allocation threshold but would need to lose 5640 votes before losing a seat to National.
In some elections, the results have been much closer to the Sainte-Lague thresholds. In 2008, Labour’s 796,880 votes gave them 43 seats in parliament. But an increase of just 39 votes to 796,919 would have given the party 44 seats and dropped National from 58 seats to 57.
Fifty-seven seats would still have enabled Sir John Key to form a government, but a 39-seat majority in an electorate race would almost certainly have triggered a recount.
In 2002, if United Future had got 503 more votes they would have taken a seat off National and in 2020 Te Pāti Māori only needed to lose 572 votes to drop back to one seat giving the other to Labour.
These “party vote margin” calculations assume an error impacts only one party. The real situation is more complicated, but in this election, the errors have impacted National by 502 more votes than Labour, the next most impacted party.
A party secretary can request a full recount of the party vote by paying a $92,000 deposit. This Herald analysis suggests that if a party is within 500 votes of a seat allocation threshold this would be money well spent and it would certainly be worth considering if a threshold was within 1000 votes.
However, perhaps it would only really be worth risking public anger over the delay if the outcome could change who got to form a government.
