Proportional representation: what it is and how it works


SINCE 1921 Ireland has been using a voting system in elections to which, it appears, we have become strongly attached. Twice the Irish people in referendums have rejected attempts to replace it with the British system.

We know it simply as “PR”, or proportional representation, but more correctly it is the mouthful “proportional representation by the single transferable vote (STV) in multi-seat constituencies” .

We share it with Malta, some elections in New Zealand, Australia and India and, now, Assembly elections, EU and local elections in Northern Ireland and local elections in Scotland.

The system allows voters the maximum choice of candidates, even within parties, while assuring both proportionality and local representation.

Although distributing seats to parties in a way that reflects pretty closely their actual vote share, STV does so less accurately than a truly proportional list system, such as Israel’s national list, or a constituency/regionally based partial top-up list system, such as Germany’s.

But it is far more accurately reflective of popular feeling than the British first-past-the-post system. Not least among its virtues is the vital sense of ownership of TDs by voters that arises from the reality that most voters will actually see their first preference candidate elected.

In the 2007 Scottish STV local elections, for example, 74 per cent of voters elected their first-choice candidate; while in 2005, not untypically, two-thirds of MPs returned to Westminster did not have majority support from local voters.


Simplicity itself. Voters cast their ballot by numbering their candidates 1,2,3 etc in the order they prefer them. Any number of preferences can be listed, with lower preferences not coming into play until the higher ones are either elected or eliminated.

That means, for example, it is quite safe on a ballot where there are 10 candidates to mark one’s most hated candidate 10 and vote up all the way through the list of least-preferred until one reaches one’s favourite at No 1 (my wife’s preferred method of casting her vote). Indeed, the most efficient way of contributing to ensuring someone is not elected ahead of your favourites is to vote all the way down the list.


Central to counting STV is the notion of the “quota” – this is the number of votes that guarantees a candidate’s election and its size depends on the number of seats in a constituency. If there is only one seat, clearly the proportion of votes a candidate requires to be elected, the quota, is half plus one, 51 per cent, as only one candidate can possibly achieve this.

In a two-seater, the quota is 34 per cent – 34+34 = 68, leaving only a possible total of 32 per cent for another candidate. In a three- seater, it’s 26 per cent, a four seater, 21 per cent. The formula for calculating the quota is thus:

                                                            Total Valid Poll   +1


After the first count is made of all the candidates’ first preferences, the returning officer deems elected those candidates who have already crossed the quota line.

The number of votes by which the quota is exceeded is the surplus. In order not to waste these votes, the returning officer then distributes a share of these to the candidates’ next preference in proportion to the voters’ wishes – if a surplus of 100 votes arises for candidate X, a quarter of whose second preferences go to Y, then Y receives an extra 25 votes.

When the surpluses have been transferred, or there is none to transfer, the returning officer then eliminates the candidate with the lowest vote (several may be eliminated at once if their total vote could not affect the outcome of subsequent counts).

All the eliminated ballots are then distributed at full value to the next available preference, disregarding preferences for candidates already elected or eliminated.

The process is then repeated again and again until enough candidates reach the quota, or until eliminations leave only one candidate for the last place who is deemed elected without reaching the quota.


On election night as the counts come in, the joy for election junkies lies in guestimating the final results from the early figures.

By totting up a party’s share of the votes and dividing it by the quota, a rough indication can be had of how many seats they should take.

Mix in a bit of local knowledge, gossip and some political instinct about new transfer patterns and you have a psephologist’s heaven, the makings of the best of race nights.

Over two quotas and two seats are very likely to be up for grabs, but, in practice, 1.6 quotas is also very likely to get two seats, particularly if a potential coalition partner has, say, a third of a quota going begging.

Take Cork South West in 2007: Fine Gael took two seats with only 1.44 quotas (Labour had 0.4 quotas).

Some candidates can get elected with as little half a quota if they are lucky with transfers – Labour’s Ciarán Lynch last time took a seat with an initial 0.56 of a quota (Cork South Central) courtesy of Green, PD and Fine Gael transfers.

And Cyprian Brady (FF, Dublin Central) broke electoral records by getting elected on the lowest ever initial vote of 2.7 per cent, courtesy of Bertie Ahern’s whopping surplus (FF – 2.2 quotas). It’s unlikely to happen again.

Poor transfer discipline between candidates from the same party or an inability to spread the first-preference vote evenly between candidates, can cost parties dear and is likely to do so this time for Fianna Fáil.

Despite taking 2.9 quotas, Fianna Fáil in Limerick city in 2007 secured only two seats because of the size of Willie O’Dea’s first preference vote – 2.3 quotas.

An even first preference distribution between the three candidates would have easily secured the third seat.