The Single Transferable Vote (STV)

STV has long been advocated by political scientists as one of the most attractive electoral systems, but its use for legislative elections has been limited to a few cases—the Republic of Ireland since 1921, Malta since 1947, and once in Estonia in 1990. It is also used for elections to the Australian Federal Senate and in several Australian states, and for European and local elections in Northern Ireland. It has been adopted for local elections in Scotland and in some authorities in New Zealand. It was also chosen as the recommendation of the British Columbia Citizens’ Assembly.

The core principles of the system were independently invented in the 19th century by Thomas Hare in Britain and Carl Andræ in Denmark. STV uses multi-member districts, and voters rank candidates in order of preference on the ballot paper in the same manner as under the Alternative Vote system. In most cases, this preference marking is optional, and voters are not required to rank-order all candidates; if they wish, they can mark only one.

After the total number of first-preference votes are tallied, the count then begins by establishing the quota of votes required for the election of a single candidate. The quota used is normally the Droop quota, calculated by the simple formula:

Quota = (votes / (seats +1)) +1

The result is determined through a series of counts. At the first count, the total number of first-preference votes for each candidate is ascertained. Any candidate who has a number of first preferences greater than or equal to the quota is immediately elected.

In second and subsequent counts, the surplus votes of elected candidates (i.e. those votes above the quota) are redistributed according to the second preferences on the ballot papers. For fairness, all the candidate’s ballot papers can be redistributed, but each at a fractional percentage of one vote, so that the total redistributed vote equals the candidate’s surplus (the Republic of Ireland uses a weighted sample instead of distributing fractions). If a candidate had 100 votes, for example, and their surplus was five votes, then each ballot paper would be redistributed according to its second preference at the value of 1/20th of a vote. After any count, if no candidate has a surplus of votes over the quota, the candidate with the lowest total of votes is eliminated. His or her votes are then redistributed in the next count to the candidates left in the race according to the second and then lower preferences shown. The process of successive counts, after each of which surplus votes are redistributed or a candidate is eliminated, continues until either all the seats for the electoral district are filled by candidates who have received the quota, or the number of candidates left in the count is only one more than the number of seats to be filled, in which case all remaining candidates bar one are elected without receiving a full quota.

Advantages and disadvantages of STV

Advantages of STV

The advantages claimed for PR generally apply to STV systems. In addition, as a mechanism for choosing representatives, STV is perhaps the most sophisticated of all electoral systems, allowing for choice between parties and between candidates within parties. The final results retain a fair degree of proportionality, and the fact that in most actual examples of STV the multi-member districts are relatively small means that a geographical link between voter and representative is retained. Furthermore, voters can influence the composition of post-election coalitions, as has been the case in the Republic of Ireland, and the system provides incentives for interparty accommodation through the reciprocal exchange of preferences between parties.

STV also provides a better chance for the election of popular independent candidates than List PR, because voters are choosing between candidates rather than between parties (although a party-list option can be added to an STV election; this is done for the Australian Senate).

Disadvantages of STV

The disadvantages claimed for PR generally also apply to STV systems. In addition:

• STV is sometimes criticized on the grounds that preference voting is unfamiliar in many societies, and demands, at the very least, a degree of literacy and numeracy.
• The intricacies of an STV count are quite complex. This has been cited as one of the reasons why Estonia decided to abandon the system after its first election. STV requires continual recalculations of surplus transfer values and the like. Because of this, votes under STV need to be counted at counting centres instead of directly at the polling place. Where election integrity is a salient issue, counting in the actual polling places may be necessary to ensure legitimacy of the vote, and there will be a need to choose the electoral system accordingly.
• STV, unlike Closed List PR, can at times produce pressures for political parties to fragment internally because members of the same party are effectively competing against each other, as well as against the opposition, for votes. This could serve to promote ‘clientelistic’ politics where politicians offer electoral bribes to groups of defined voters.
• STV can lead to a party with a plurality of votes nonetheless winning fewer seats than its rivals. Malta amended its system in the mid-1980s by providing for some extra compensatory seats to be awarded to a party in the event of this happening. Many of these criticisms have, however, proved to be little trouble in practice. STV elections in the Republic of Ireland and Malta have tended to produce relatively stable, legitimate governments comprising one or two main parties.