How your vote works
The general election is conducted on the principle of Proportional Representation, using the Single Transferable Vote System. The elector casts a single transferable vote, i.e. a vote given in such a way as to indicate the voter's preference for candidates in order of choice.
If the voter so indicates, this vote can be transferred from a choice to a next choice when it is not required to give the prior choice the necessary quota of votes to secure election; or when, owing to the poor support given for the prior choice, that choice is eliminated from the contest. The voter does this by placing numbers against the names of the candidates on the ballot paper in the order of his / her choice. He/She need not vote for all the candidates, but must number preferences continuously (1,2,3 etc)
To ascertain who has been elected, votes are initially sorted according to first preferences, and any candidate who obtains the "quota" or more is elected.
The quota used in Irish elections is the "Droop Quota" - so called because it was first propounded by H.R. Droop in 1869. It is the smallest number of votes that suffices to elect enough candidates to fill all the seats being contested, while being just big enough to prevent any more being elected. It is expressed in the following formula:
Quota = ( No. of Valid Votes / No. of Seats + 1 ) + 1
A simple example:
Electorate: = 12,000
Seats to be filled: 4
Valid Poll: = 10,000
Quota = [ (Valid Poll) 10,000 / Seats (4 + 1) ] +1 = 2,001
If four candidates each get 2,001 votes, then only 1,996 votes remain to be distributed among the remaining 3 candidates and, therefore, it is impossible for more than four candidates to be elected. On the other hand, the percentage of the total valid poll necessary to elect a candidate is not 25% but very slightly over 20%.
If, as is usually the case, the first count does not result in all seats being filled, a process of transferring votes takes place in subsequent counts until this result is achieved. First, the "excess votes" of any candidate who exceeds the quota are distributed proportionately to the second or next available choices of his supporters.
When no surpluses remain to be distributed and there are still seats to be filled, the candidate with the fewest votes is eliminated and his/her votes are redistributed according to the next available preferences indicated. This process of counting continues until all vacancies have been filled. At times, a candidate who did not achieve the quota, as all other candidates have either been elected or eliminated may fill the final place.