For those who are interested, Supplementary Member has the same system of electorate and list seats, but, unlike MMP, the two are not connected. List seats are filled with the party vote and electorate seats with the electorate vote. If you get 10% of the party vote you get 10% of the list seats, 1% gives you 1% of the seats. There is no threshold.

If this system is weighted towards electorate seats (e.g. 70 electorate and 30 list seats), then it tends to act much like FPP and favours large parties. If you have less electorate seats and more party seats, this tends to reduce the advantage of large parties.

As an exercise in how it would work, I have taken yesterday’s election results and put it into an SM system under the following assumptions.

• There are 50 electorates and 100 list seats giving a parliament of 150. I think the system seems fairest at 1 electorate to 2 list seats. I also can’t see less than 50 electorate seats working very well (the electorates can’t be too large) – hence the 150 seats.
• Anything above 0.5% will get you a seat. 0.5% or less will not. 4.50% will get you 4 seats 4.51% will get you 5. Rounding errors may give you 1 or 2 seats too many or too few but over/underhangs will be small.
• I have assumed 5 Maori seats (10% of electoral seats) and allocated them to the Maori party. It is possible that Labour could have won one or two of these, but I have assumed not. Note that Maori allocated electoral seats tend to skew this result in favour of Maori.

The results look like this (click for a larger image)

2008 MMP Election as an SM Election

What I found most interesting is how similar the vote would be for most parties. National/Act would still govern with a three seat majority (five including united future). New Zealand First would be back and those 4% of votes would not be wasted. Even Bill or Ben would have got in!

Of all the voting system, I think this is the fairest, while still retaining the immediacy of electoral representation. Pure proportionality sounds nice, but the MPs elected are not chosen by the public (and often not even by party members) leaving New Zealanders without direct access to parliamentary members. In a referendum, SM will be getting my vote, as long as at least 50% of parliament is proportional.

Related posts:

1. And Seats For All…
2. Viewpoints
3. Getting Away With Nothing