UK referendum on the election system

[happydork]

Posting at the_future_modernes's request.

On Thursday 5th May, there is a referendum being held in the UK on changing the system for electing members of parliament.

The full text of the question will be

At present, the UK uses the “first past the post” system to elect MPs to the House of Commons. Should the “alternative vote” system be used instead?

First Past The Post (FPTP), the current system, works as follows:

The voter: Marks their first choice candidate.

The returning officer: Counts how many votes each candidate has. The candidate with the greatest number of votes wins.

Alternative Vote (AV), the proposed system, works as follows:

The voter: Puts the candidates in order of preference.

The returning officer:
1) Counts how many first choice votes each candidate has. If one candidate has over 50%, that candidate wins. If not, the candidate with the least number of votes is eliminated from consideration.
2) In each subsequent round, each vote counts for the voter's favourite candidate who is still in the running. If one candidate has over 50% of the vote, that candidate wins. If not, the candidate with the least number of votes is eliminated and the procedure is repeated.

(If this is not clear, a worked example of AV may be helpful.)

I strongly recommend A Guide to the Alternative Vote (pdf) by Roger Mortimore, Ipsos MORI SRI Director of Political Analysis as a clear, interesting and reasonably unbiased guide to the debate.

I've also put together my own (biased) collection of links.