How to make the PR system work for you

A guide to proportional representation:The system of proportional representation used in Ireland can be difficult to explain, but it is very simple to use. Voting simply involves filling up the ballot paper by ranking the candidates, 1,2,3 and so on, in order of preference.

To use the vote most effectively, it is best to vote right down the paper giving a preference to everybody, but it is not essential to do so and the voter can stop anywhere. The important thing to remember is that a lower preference can never interfere with a higher one so there is no dilution of the vote by carrying on preferences.

It is essential, though, to use numbers to list the candidates in order of choice and on no account put "X" opposite the names of candidates.

The easiest way to approach voting is to rank the candidates you would like to see elected in the order of preference. Having done that, continue your preferences by ranking the people you don't like, down to the candidate you positively detest, giving him or her your last preference.

In many cases the preferences are never examined at all and the vote will stay with your number one choice right through the count. The crucial thing is that a voter's second preference only comes into play if the number one choice is elected or eliminated. The same thing applies down to the last preference.

The way the count will work is that all the ballot papers for a constituency will be sorted in the morning to check that the number of votes in each ballot box tallies with the number actually put into the box by voters the previous day.

It is during this exercise that the tallymen and women scrutinise the ballot papers from behind a barrier to estimate where the votes are going.

This has now been brought to a fine art and the parties generally co-operate with each other and use computers to make a prediction.

When all the votes are sorted the returning officer makes a calculation about the quota. This is worked out by dividing the total number of valid votes by the number of seats, plus one. One is then added to the result.

For instance, suppose 40,000 valid votes are cast in a four-seat constituency. The number of seats plus one is five, so 40,000 is divided by five to give 8,000. One is then added to the figure to give a quota of 8,001 to ensure that there could not be five quotas. The first count will then take place, with the result in early evening. If any candidate gets a quota or more on the first count, they will be elected. The next thing that will happen is that the surplus votes of any candidate with more than a quota will be distributed.

Taking our earlier case where the quota is 8,001, suppose that one candidate comes in over the quota with 10,001 votes and thus has a surplus of 2,000. That candidate's entire 10,001 votes will then be counted and the second preferences totted up.

Suppose that candidate X gets 50 per cent of the number twos, he or she will then get 50 per cent of the surplus which in this case would come to 1,000 votes. A bundle of 1,000 votes is then physically transferred to X's pile.

When the first count surpluses are distributed, the candidate with the lowest number of votes is eliminated and his number 2s are transferred.

If the number 2 goes to a candidate who has already been elected or eliminated, it is passed to the next available candidate still in the contest. Again the votes are physically transferred. The process of elimination continues until all the seats are filled.

There is one added factor in the count. A candidate who is pushed over the quota with transfers in the middle of the count has a surplus to be distributed. Unlike a first count surplus, when all the number 2s are examined, a surplus on a subsequent count is a random selection of votes from the last bundle won by a candidate.

For instance, if candidate Y gets 7,000 votes on the first count and eventually ends up being pushed over the quota on a later count with, say a transfer of 2,001 from an eliminated candidate, it means that in our hypothetical constituency he will have a surplus of 1,000. The last 1,000 votes added to his pile will then be transferred to the next available preference on the ballot paper.