I happen to find voting systems to be of interest and I do indeed have a favoured voting system but this piece is not for me it is for people who have vaguely heard of the coming referendum and are curious or confused about what AV or FPTP is and what it has to do with them.
First what is the current voting system used in the UK:
The system used in the UK general elections is called First Passed The Post aka FPTP; under this system the united Kingdom is separated into electoral areas called constituencies (to find yours you can go to (http://news.sky.com/skynews/Election/Map) . Under FPTP each constituency is represented in parliament and served by one MP (Member of Parliament).
Under FPTP when electing the MP for your constituency; you are ask to place a single vote next to the candidate (person standing for election) of your choice. You can only vote once and this vote is counted by electoral officials on voting night and the candidate with the most votes is elected to be the MP representing that constituency.
Once a MP is elected he is supposed to represent his whole constituency regardless of their personal party affiliations and to assist their constituents regardless of their party affiliation. To find your MP you can go to (http://findyourmp.parliament.uk/).
What is the proposed new voting system?
The proposed new system is called Alternative vote: The alternative vote system is still based on the ideal of one representative per constituency but instead of casting one vote you are asked to number the candidates in order of preference (starting at one). You do not have to mark a preference against every candidate but can for all if you wish.
These votes are called preferences, so the candidate you number one is referred as your first preference, the one you put two next to is your second preference and so on. Unlike FPTP there is no numerical majority, instead AV seeks to establish a percentile majority. In layman’s language this means that in order for a candidate to be chosen they require more than a majority of votes (as compared to other candidates) they require over fifty per-cent of the votes cast.
Therefore if there were 10,000 votes and candidate A got 5,001 first preference votes he would be elected, however, if candidate A got 5,000 and candidate B got 4,000 and candidate C got 1,000 no single candidate would have the fifty per-cent required to get elected and this is where the second (and lower) preferences kick in.
Under AV the lowest candidate (the candidate with the least 1st preference votes) would be eliminated and the second preference of those who voted for the eliminate candidate as their first preference would be counted (They would in reality be treated as if they were first preference votes), there other preferences would also be transferred to candidates accordingly. This processes, lowest candidate eliminated, votes re-distributed until one candidate got the fifty per-cent majority required.
This may sound very complex, however, from the voters perspective all that is required is that you list candidates in the order you would chose them to be your candidate all the rest will be taken care of care of the electoral officials and after all of this voting takes place we are still left with a single MP for an single constituency