The original of this post by Rob Salmond is here.
Last night, via One News, the public became aware that the Greens had proposed a pre-election coalition with Labour, but Labour had rejected it.
To understand the contours of the possible deal, you need to know a little about pre-electoral coalitions in general:
First, pre-electoral coalitions are quite common. According to Penn State political science professor Sona Golder, about 20% of post-WW2 elections in advanced democracies result in a government that was conceived in a pre-electoral coalition. There have been over 240 pre-electoral coalitions of parties running together in advanced democracies since 1946. So there is nothing weird about the Greens’ proposal.
The proposal for a proportional cabinet, by the way, is also entirely normal in other PR countries. The political scientists have even christened a law called Gamson’s Law that describes this very common method for sharing out cabinet seats.
Second, however, pre-electoral coalitions are more common in electoral systems that are not quite like New Zealand’s. New Zealand has an especially pure, fair form of proportional representation (so long as you can pull 5% of the vote). A single national district for sharing out list seats, along with the Modified St Lague method we use for assigning them, are the elements that make New Zealand’s system so fair.
In many other proportional systems, there are various ways to provide disproportional rewards to the single largest party or bloc. Sometimes these are based on electoral formulas or districting schemes tilted towards the largest party/group, sometimes there are even explicit bonuses. Prof Golder finds that it is in electoral systems featuring more of these Biggest Group Advantages where pre-electoral coalitions are most effective, and most widely used.
The basic idea here is that a pre-electoral deal is an especially good idea if it gives the group of parties a leg-up in the mechanical process of transferring votes into seats.
New Zealand does not have any of those advantages for the Biggest Group, so the incentive to form a pre-electoral deal, rather than just wait and form a government post-election, instead, is not as strong as in many other countries.
So while the Greens’ offer is nothing unusual internationally, New Zealand’s comparatively fair electoral system doesn’t provide Labour much incentive to accept it. Which, I think, makes Labour’s rejection of the proposal much less noteworthy.