Mixed-Member Proportional (MMP)
The most important feature of MMP is that it is proportional: seats in the parliament are assigned to parties in proportion to the percentage of the national vote that each party receives. The actual way that is worked out is by the Sainte-Laguë formula, and the final result is, indeed, pretty proportional. There are, however, some twists and turns.
There are approximately (see below) 120 Members of Parliament, which works out to 0.83% of the vote per MP. The first twist is that there is a threshold of 5%, i.e., in order for a party to get any Members of Parliament, it must get at least five percent of the vote. This stops the parliament from being fragmented into many small parties, Italian style, but whether it's a fair barrier to participation is questionable, especially as preferential voting is not used. As we'll see, this barrier exists for some, but not for others.
The next twist is that rather than being just a party-centred proportional system, there is also a level of regional representation built into MMP. Seventy MPs are, in fact, "Electorate" MPs: they are elected to represent a particular electorate by a first past the post vote. This doesn't mess with the proportionality of the system (mostly: see below!), because each Electorate MP counts against the party's total allocation. The rest is made up from "List" MPs.
So at the ballot box, each voter has two choices to make: the party they want to vote for and the local electorate candidate they want to vote for; one voter, two votes. To first approximation, the electorate vote is irrelevant: the total number of MPs the party gets is determined by the party vote, exactly which electorates they represent -- or whether they come in on the List -- is a matter of shuffling the chairs. But for small minor parties the electorate vote can be very important: winning an Electorate seat means dodging the 5% threshold.
In the 2008 election, for example, the ACT party received 3.65% of the party vote, less than the threshold; but one of its candidates, Rodney Hide, won the seat of Epsom, thus defeating the threshold. ACT's party vote was enough to elect 4 additional MPs. Another party, New Zealand First, received 4.07% of the party vote, but won no Electorates, and therefore received no MPs. The Maori Party only got 2.39% of the party vote, but won 5 Electorates, so its representation in the parliament was much larger than its party vote required (3 seats)! This, by the way, is why the number of MPs is not fixed. The Maori Party excess means there are currently 122 MPs; an "overhang" of two. So once again we see that concentrated regional support trumps broad, thin support.
The main problem with this is not so much the discrimination between parties (though I'm sure Winston Peters would disagree), as the discrimination between voters. As we've seen, the "one voter, two votes" of MMP is really just "two ticks, one vote" for most voters. But some voters -- those in the Maori Seats and the Good People of Epsom -- actually do get two votes!
Renowned Aussie psephologist Malcolm MacKerras explained this a worthy rant some time ago, and this election this exploit is very much in the public mind. However, the complaint being made by the SM proponents is very different. What upsets them about MMP is that it is difficult to get rid of a particular parliamentarian. If they lose their Electorate, because they're out of favour with their constituents, but are still in favour with their party then they come into parliament as a List MP. This is a consequence of the party-centred philosophy of MMP, as opposed to the candidate-centred philosophy of STV.
MMP is designed with the expectation that voters vote for a party, whilst STV allows voters to vote for an individual. While it is true that modern politics in much of the world, and certainly in New Zealand, is based on the party, objections to particular members are not that uncommon. The example that springs to mind is Larry Anthony, turfed from the seat held by his father and his grand-father despite the overall swing to his party. This would be almost impossible in MMP. The voters' inability to rid themselves of unpopular politicians is a fair complaint, however the correct solution is to opt for STV, not SM.
First Past the Post
- Pro: Voters feel they understand it.
- Con: They don't.
- Pro: Can vote for the candidate you want.
- Con: Overwhelmingly favours the largest parties.
- Pro: Better than FPP.
- Con: Not better enough.
- Pro: Preferential and (approximately) Proportional.
- Con: Complicated.
- Pro: Proportional representation.
- Con: Not preferential, favours voters in some electorates.