Explainer
Explainer: How MMP seat allocation actually works
Party vote, electorate vote, the 5 percent threshold and the Sainte-Laguë formula — a plain-language guide to how New Zealand's Parliament is filled.
Every three years New Zealanders cast two votes — but it's the party vote that does most of the work. Here is how the seats in Parliament are actually allocated under Mixed-Member Proportional representation.
Two votes, two jobs
Your electorate vote chooses the local MP for your seat. Your party vote decides the overall share of seats each party gets in Parliament — and it is by far the more powerful of the two.
The threshold
To share in the party-vote seats, a party must either win at least 5 percent of the nationwide party vote, or win at least one electorate seat. Miss both, and the party's votes are effectively set aside.
The formula
Seats are divided using the Sainte-Laguë method, which repeatedly divides each qualifying party's vote by a rising sequence of odd numbers and hands out seats to the highest resulting quotients. It is designed to keep each party's seat share close to its vote share.
- Electorate seats a party wins are subtracted from its entitlement first.
- The remainder is filled from the party's list.
- An "overhang" can occur if a party wins more electorates than its party vote entitles it to.
The upshot: to understand who governs, watch the party vote and the threshold — not just the electorate contests.
Filed by
Priya Naidu
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