Voters in the United Kingdom were given the opportunity on 5 May 2011 to choose between keeping the current First Past The Post (FPTP) voting system, or switching to the Alternative Vote (AV) system. They chose to retain FPTP.
In the First Past The Post system, the elector marks their preferred candidate on the ballot paper. The candidate with the most votes wins. In the Alternative Vote system, the elector numbers the candidates in order of preference. If a candidate gets more than half the votes, that candidate wins. Otherwise, the candidate that came last is eliminated, and those votes are reallocated to the second preferences of those who voted for that candidate. The process continues until one candidate has at least half the votes.
Suppose there are three candidates, whom we’ll call Red, Blue and Green. Red is the first choice of 45% of voters, Blue is the first choice of 46% of voters, and Green is the first choice of 9% of voters. The Green voters know that their candidate has little chance of getting in. Two-thirds of Green voters support Red as their second choice, and one-third support Blue as their second choice.
With Alternative Vote, neither Red nor Blue has half the votes. So Green, having come last, is eliminated. The second preferences of those who favoured Green are then distributed to the other candidates. Most Green voters preferred Red to Blue. Red gains an additional 6% of the total vote, to end up with 51%. Blue gains an additional 3%, to end up with 49%. Red is declared the winner. This reflects the will of the people, because more people prefer Red to win than prefer Blue to win.
With First Past The Post, Blue gets 46% of the vote and is declared the winner. However, Blue is not supported by the majority. Overall, more people support Red than Blue. It just happens that the Green candidate was particularly popular with those who lean towards Red, and diminished Red’s vote. So First Past The Post did not produce a fair result.
Knowing that this is how First Past The Post works, some of Green’s supporters would have voted for Red instead of Green, just to keep Blue out of office. This is called tactical voting, and complicates things for the elector because they don’t know whether they will need to vote tactically to avoid “wasting” their vote, or whether they will be able to vote for
the candidate they genuinely prefer.
The primary advantage of Alternative Vote is that the winning candidate is always preferred by more voters than the runner-up. The secondary advantage of Alternative Vote is that each voter is free to express their genuine preference, without the risk that their vote will become useless by doing so.
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