May 4, 2011 10.40 am This story is over 155 months old

How the alternative vote works

Referendum: AV is simple and something everyone should get to grips with before they vote on Thursday, May 5.

Contrary to the view of Prime Minister David Cameron, the alternative vote (AV) is not something “only a few number crunchers in Westminster understand”.

It’s simple and something everyone should get to grips with before they vote in the May 5 national referendum on introducing AV for British general elections.

This is only the second national referendum Britain has ever seen. The first, in 1975, asked if Britain should stay in the European Economic Community (EEC).

In our current electoral system of first-past-the-post, voters choose one candidate. The winner of the election is then the candidate with the most votes. This often means candidates are elected with a minority of support in a constituency.

Candidates can win with support of just 30% of the turnout, leaving 70% without someone they want.

Under AV a candidate must win over 50% of the votes in order to be elected.

Voters are asked to rank the candidates in numerical order of preference. If there are five candidates you do not have to write a number next to every single one. You can just choose one candidate, like under our current system of first-past-the-post.

Or you can choose a couple and leave the candidates you really wouldn’t want winning blank.

The results are decided during “rounds” of voting. The final result is only reached once a candidate passes the 50% threshold.

So voters’ first-preferences are counted. If no one reaches the threshold, this is where voters’ second-preferences come in.

Assuming the threshold wasn’t met, we proceed to the second round of voting.

The candidate with the fewest first-preference votes in the first round is eliminated. The voters who listed this candidate as their first-preference then have their second-preferences distributed on top of the surviving candidates’ original first-preference votes.

If no one reaches the threshold in this second round of voting, the process starts again and we move on to the third round. This elimination and redistribution continues, round by round, until a candidate reaches the threshold.

If the threshold is not met by the final round, when only two candidates remain, then it is simply the candidate with the most votes in that round who wins.

Still uncertain on how AV works? This video may help.