Legal Beagle by Graeme Edgeler


Alcohol Game Theory

At 5:30 this evening, the House of Representatives will hold an "election" on the alcohol purchase age.

This is not the way it usually does things. I suspect that it is not the way it has ever done things.

The House historically decides between two options. The law, or a provision in a bill, is one way, and someone proposes changing it: the House decides between supporting that proposal to change it, or not supporting it. It just goes through a series of simple binary choices: those who are in favour will say 'aye'; those opposed will say 'no'.

Not so on this evening's vote on the alcohol purchase age. Instead, MPs will hold an election between three options:

  • setting the alcohol purchase age at 18 for both on-licences and off-licences
  • setting the alcohol purchase age at 20 for both on-licences and off-licences
  • setting the alcohol purchase age at 18 for on-licences but 20 for off-licences (a split age)

If no option secures a majority of votes cast at this election, a personal vote will be held between the two highest scoring options.

Simple, right? This will mean whatever option is chosen will be supported by a majority of MPs? Well, no, says the electoral system nerd in me is screaming "but what about the Condorcet criterion?" Because the system they have agreed to adopt, may mean that the option that would win majority support in a vote between each of the other two, may be discarded.

I think it reasonable to assume that most (although not necessarily all) MPs who favour an alcohol purchasing age of 20, will think that a split age is preferable to setting it at 18.

And probably also reasonable to assume that the MPs who favour setting the age at 18, will think a split age is preferable to setting it at 20.

And looking at this, you might think that, if the no one option has a majority, then a consensus could form around a split age, as the lesser of two evils for MPs supporting a straight 18 as the alcohol purchasing age, and MPs supporting a straight 20.

But that might not be the result. Imagine the following made up scenario:

  • 50 MPs favour 18
  • 40 MPs favour 20
  • 31 MPs favour a split age

Under the procedure the House has adopted, split age drops out after the first vote and all MPs get a second vote between the option of setting the age at 18 or 20, with the 31 MPs who supported split age choosing between the other two options, and putting one or other over the top.

But look at what these numbers would actually mean (adopting my assumptions above, about supporters of 18 and 20 preferring compromise to defeat):

  • By a vote of 71 to 50, MPs would prefer a split age over an age of 18
  • By a vote of 81 to 40, MPs would prefer a split age over an age of 20

And yet what we would get would be an age of 18 or 20, even though a parliamentary majority would oppose such a law. As much as I personally favour "keeping it 18", if none of the three options has a majority on its own, what results will be a compromise, and it should be the compromise which actually has majority support.

I quite like one aspect of the procedure the House has adopted: the debate on the alcohol purchasing age is being conducted as an "in principle debate", and after the votes occur, the debate on the rest of the bill (it's quite extensive) will be deferred and any amendments necessary to implement the decision on the alcohol purchase age will be drafted by the Parliamentary Counsel Office. This should mean that the drafting of the law will actually reflect the option the House chooses. Alcohol bills, as a result of past conscience votes, have sometimes come out the the legislative process worse for wear. More than once, the law has needed swift amendment, when provisions added during the Committee Stage have added problems not able to be addressed in the heat of debate. Hopefully, this process means similar problems can be avoided.

While Leader of the House Hon. Gerry Brownlee did give a clear explanation of the form for the "election", the exact process by which the first vote will take place hasn't been publicly stated - there are, after all, only two doors for MPs to walk through when voting. My preference would be for what the US Senate would call a "roll-call" vote, where MPs are called upon to state their preference in the House. This is the process that Standing Order 19 provides for the election of Speaker if there are more than two nominees (the same process whereby a majority is needed, and if none achieved, the lowest polling option drops out, is adopted there). Although it appears that this public process may not be adopted: in response to a twitter query from me about the holding of a roll-call vote, David Farrar replied "No, voting will be in the noes lobby".

Ref: Gerry Brownlee's statement in the House about the process to be adopted for the vote:

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