So what difference would Alternative Vote make?

On May 5th, voters in Britain will vote in a referendum to choose between sticking with the existing First Past The Post (FPTP) voting system or switch to using the Alternative Vote(AV).

Under the AV system being proposed, you vote by ranking the candidates in order of preference, and you’ll be able to rank as few or as many of the candidates you like. So, in a constituency where the Tories, Labour, Greens and Lib Dems were standing, a voter could put their first preference for say the Green Party candidate, their second for the Lib Dem candidate and ignore the Tory and Labour candidate.  When votes are counted, one or more rounds of counting are required:

• First of all the first preference votes are counted. If a candidate receives a majority of votes then that candidate wins.
• Otherwise, the lowest placed candidate is eliminated and their votes restributed according to the second preference for a second round of counting. This process repeats until a candidate receives a majority of the votes for a given round.
• Should someone who’s candidate has been eliminated not have expressed a preference to allow redistribution in a given round, their vote gets eliminated in that round.

The aim is to try and ensure that the winning candidate has over 50% of the votes cast, but in practice this can only be guaranteed if every voter gives a preference to every candidate. Australian elections often require this but the proposed British system will not. Thus it will be possible for someone to win without a majority of all votes cast. An extreme example is if all voters only give a first preference then a mere plurality of first preferences will suffice. More probable is someone’s first and second preference candidates being eliminated and their vote being set aside.

Nevertheless it can  be argued that AV gives the following advantages over FPTP:

• Only those who get a large majority of first preference votes can consider their seats “safe”.
• Voters can vote for their favourite party on the first preference and use their second preference to avoid “splitting the vote’. E.g. a UKIP voter could vote UKIP for first preference with the Tory candidate as a second preference to ensure Labour don’t get in, where under FPTP they might let Labour in by voting UKIP rather than Tory.
• Would-be MPs would need to broaden their appeal since simply obtaining a purality of first preference votes is unlikely to be sufficient to win, they will need to campaign for second and third preferences. This would reward MPs who develop strong constituency backing beyond their party boundaries and thus encourage more independence of MPs from parties.

For these reasons, I believe AV will be an improvement over FPTP and will give voters more power over the final outcome.

However it can be argued that AV might not really make much difference, for example John Curtice argues that the following points suggest AV might not make much difference:

• most of the time people are likely to put their first preference down as the same party they would previously have marked X against.
• even where 2nd and subsequent preferences are counted, because only the preferences of the lowest place parties are redistributed, there’s a limit on the impact of such redistribution. E.g. the two most popular candidates get 70% of first preferences between them, that only leaves 30% for redistribution.
• in the end AV is not proportional and will still tend to reward large parties as FPTP does.

Whilst in the short-run, the impact may be modest, I think this underestimates the long-run impact of a switch to AV for two reasons:

• Curtice bases much of his argument on studies of voter behaviour in mock AV elections. However as voters get used to how AV works they may well alter their behaviour, making more effective use of the second and subsequent preferences over time. Extrapolating behaviour from voters in mock exercises does not cater for this possibility.
• The incentives for politicians will change, they will have to appeal to a broader range of their constituents than before in order to win and keep winning. They will also be disincentivised from attacking a section of their electorate lest they need the second preferences to win.

Thus, I think AV will lead to a long term evolutionary change in how British elections are fought towards more broad based appeals and less divisive politics, albeit still within a majoritarian framework where large blocks of MPs form a government after each election.

That said, AV does have many flaws, e.g.:

• It’s only the second and subsequent preferences of eliminated candidates that get taken into account in each round and the second and subsequent preferences of the two most popular candidates on first preference will only rarely get used.
• It is also quite possible that a larger majority would exist for e.g. the candidate placed first on first preferences if you took all second preferences into account than for the eventual winner.
• Finally, tactical voting is not eliminated under AV, where there may be occasions where it makes sense to put your first preference tactically against a party in order to increase the chances of defeating your least favoured party or even to increase the chances of your favoured party winning. That said, it’s difficult to predict how such tactical voting will work out in practice and there’s less need of it under AV than under FPTP.