Single transferable vote

The system of transferable Einzelstimmgebung (also preferential voting system, single transferable vote english, STV) is a proportional persons choice method to resolve the problem of invalid votes in the pure majority voting and bring about a better representation of all votes cast. In this method, multiple winners per constituency to be determined. It is used explicitly to the election of persons, not the election of party lists.

In the transferable Einzelstimmgebung a ranking of all (or some) candidates will be created by each voter. According to different calculation methods (usually the Droop quota is mentioned method used) is made ​​to be awarded seats and votes cast calculates a number of votes that is needed for election. Now the ballots according to the specified preferences to be processed. If a candidate has already chosen ( number of votes greater as a result of the Droop quota), this voice is the next candidate on the personal ranking of the voter benefit.

Likewise, the votes of non-elected candidates will now be transferred to the top rankings in the following step. The candidate with the least total votes shall be removed from all lists, the voice gets instead is the candidate who is on the list above him. Thus, both excess votes and votes for non-elected candidates are transferred to the other candidates until all the seats are occupied.

• 9.1 Impact on factions and candidates
• 9.2 Tactical Considerations for number of candidates
• 9.3 voting system criteria
• 9.4 constituency size

Dissemination

2007, the transferable Einzelstimmgebung in elections in Australia, Malta, the Republic of Ireland, was Northern Ireland used (except for elections to the British House of Commons ) and Iceland. The system is also used in some local elections in New Zealand and in local elections in Scotland. Since 2002, the transferable Einzelstimmgebung in the United States shall not be used in elections to governing bodies of Cambridge (Massachusetts ).

Designations

If the rules of the STF are used in an election in which only one person is to be selected (eg Einpersonenwahlkreise or president ), it is the same as instant runoff voting, which is not a proportional electoral process itself. Are Assign a number of seats in constituencies, the method is sometimes referred to as proportional representation through the Single Transferable Vote or STV - PR. Since Instant Runoff is no proportional representation method, it is considered by some scholars as a distinct PR -STV system. If the label STV is used, in any event, meant for usually PR -STV, so also in this article. STV is also known by other names: In Australia, sometimes referred to as " Hare -Clark proportional " method, in the U.S. it is sometimes called choice voting.

Voting

In the transferable Einzelstimmgebung (STV) of voters ranks the list of candidates according to their preferences. In other words: In addition to his most preferred candidate, he puts a "1" next to his second most preferred candidate, a "2 " etc. So the completed ballot paper contains a ranking of the candidates. An example:

Counting of votes

Determination of the rate

In STV elections a number of different rates can be used, but the most common is the Droop quota.

• Valid votes = total number of valid votes cast
• Seats = number of posts to be filled

Find winner

Put simply requires each candidate at a STV election a certain minimum number of votes - the quota - to be selected. From each candidate with more votes than either necessary, or too few in number to be elected, votes are transferred to other candidates. This process is continued until all seats are assigned. The candidates are transferred to the voices, are determined by the preferences that you have specified on their ballots the voters.

Initially, only the Erstpräferenzen be counted. Each candidate whose votes greater than the quota is immediately declared elected. His surplus votes are then transferred to other candidates. If you do not yet have reached the quota enough candidates, the candidates are eliminated gradually individually with the fewest votes and transfer their votes until enough candidates have reached the quota, so that all seats are assigned. Once a candidate is either elected or eliminated, it is excluded from the rest of counting; it can then no further votes are transferred to him (except for the Meek method). Complete the enumeration of a STV election proceeds in the following steps:

To avoid unnecessary counting, counting is not usually continued until each candidate has reached the quota, but it ends when not remain more candidates than seats to be allocated yet. If the number of votes to be transferred is not sufficient to choose someone or to change the order of the candidates in order of preference, then multiple candidates can be eliminated at once, or a surplus can be retained instead of being transferred. This is unavoidable if ballots contain a complete ranking of the candidates may be exhausted (ie not been awarded all preferences ), because then the possibility exists that not enough candidates reach the quota.

Since the transferable Einzelstimmgebung the votes for candidates who have either more votes than necessary or to be too few chosen to be transferred to other candidates, it is said that this method minimizes the number of wasted votes.

Illustration of the principle

To illustrate an STV election is sometimes compared to a choice among children in the schoolyard. When choosing the children stand behind the candidate of their choice, but no candidate can be elected if he does not gather a minimum number of children behind. Since the children know that each candidate only the votes of a certain number of peers needs to be selected, choose those that have gathered as a last behind a candidate who already has enough votes not to waste their vote, but to stand behind one another to help him win. Just change also all those children whose candidate apparently can not win. This continues until all the representatives are selected.

STV can be viewed as an automated version of this method, with the exception that the elimination of the candidate with the fewest votes sometimes disadvantaged candidates who might have still won if they had not been eliminated in the same. Every winner needs a quota of votes, rather than a specific number of children who line up behind him, and instead of the children 's preferences on the ballot papers are transferred accordingly.

Another example

Suppose that it is carried out to determine which foods should be offered at a party a vote. There are five candidates, three of whom are to be elected. The candidates are: " oranges ", " pears "; "Chocolate ", " Strawberry " and " candy ." The 20 guests of the party have given their preferences on their ballot papers in the following two tables (the first number indicates, the second represents frames ). In this election, only the first one or two preferences are displayed because the lower preferences in this case have no influence on the result.

First, the rate is calculated. When using the Droop quota, 20 voters and 3 winners to be determined, is the necessary number of votes to be elected:

The counting of votes is as follows:

Different methods of counting

STV systems differ in a number of characteristics, mainly in how votes are transferred and in the exact size of the quota, which is used to determine the winner. For this reason, there have been proposals STV as a family of electoral processes held to be regarded as a single voting procedures. Nowadays, the Droop quota is the quota most commonly used. This is ( except in rare cases ) the majority usually safe while at the same time comply with the condition that no more candidates can meet the quota are to forgive as seats. In the original conception of STV used the Hare quota ( votes / seats ), but this is now generally regarded as technically inferior option. New Zealand uses a quota, which is similar to the Droop quota.

The easiest way to transfer surpluses in STV, contains an element of chance. Systems, which are based in part on chance, are in the Republic of Ireland used (except for Senate elections ) and Malta, but also in other places. For this reason Gregory method is designed (also known as Newland - Britton or Senate rules ), turn off the accident by allowing the transfer of votes fractions. Gregory is used in Northern Ireland, the Republic of Ireland ( in Senate elections) and Australia. Both Gregory and these previous methods is, however, the problem is that they do not treat in some circumstances all voices equal. For this reason, Meeks method and Warren's method were invented. While simpler methods a counting by hand is possible to count by computer is necessary in Meek and Warren except for very small elections. Meek is currently used in STV elections in New Zealand.

The latest refinements of STV involve an attempt to resolve the problem of the successive exclusions. Successive exclusions mean that STV sometimes at an early stage of counting candidates eliminated, which would later seating can achieve when they have longer allowed to stay in the race. Procedures such as CPO -STV ( Comparison of Pairs of Outcomes by the Single Transferable Vote) and Sequential STV were invented to overcome this problem by integrating elements of Condorcet methods in STV. One known as BTR -STV method addresses the problem differently and easier than this method, simply by ensuring that no such candidate can be eliminated. None of these new methods has previously been used in a state election.

Alternates

Compared to other selection methods is the question of how casual vacancies to be filled, difficult as the results of transfers of several candidates depend. To determine a Nachrückers there are different ways: countback method that appointment, election, replacement list.

Effects and problems

Impact on factions and candidates

The use of STV can lead to a decline in the role of political parties during dialing and also to the decrease of corresponding bonds in party resulting from the choice of governments. In contrast to those proportional representation systems that use party lists, voters are not explicitly defined in STV on parties, even if there is this; voters can ignore party affiliation and put together the ranking of their preferred candidates free from candidates of different parties. Candidates can achieve electoral success by getting enough votes from voters not usually append their party, possibly by getting transmitted voices of politically related followers of other parties or by position itself in a particular subject, contrary to the party line. In contrast to the proportional representation with lists STV can be used where it is not necessarily clear stock and flows are, for example, trade unions, associations and schools in elections in organizations.

However, there are also some STV variants that strengthen the role of political parties. In the Australian Senate elections, the combination of large constituencies, elective and complete to the last preference to be completed ballot papers means that 95 % of voters follow pre- election proposals of the parties. Thus, the parties gain significant power in determining the election outcome by setting the order of the recommended candidates, both their own candidates as well as the transfers to other parties.

Since it is for a candidate not only important to get Erstpräferenzen, but also second and third preferences decreases the incentive for Negative Campaigning, as this reduces the chances of winning by supporters of other candidates second and third preferences.

Tactical Considerations for number of candidates

For parties arising tactical considerations, how many candidates should send them in an election in the race, if in choosing not fully completed ballots are required. To compete with too few candidates can lead to all candidates have already been selected in an early stage of counting votes and then be transferred to candidates of other parties. To compete with too many candidates could mean that the candidates will each receive too few Erstpräferenzen and thereby candidates who had by large second- preference support can be successfully eliminated before others are chosen and their second preferences are transferred. This effect is further enhanced if the voters do not adhere closely to the candidate of their preferred party; However, when voters select all candidates of a particular party before choosing another candidate and before entering any other preferences, then ask too many candidates is not a problem

In Malta, where voters do closely follow the party preferences, parties often provide more candidates than seats to be elected. In Australian Senate elections, voters choose similar along party lines, as it is much easier to choose the declared preferences of a party as to compile a complete list itself. In the Republic of Ireland, the main political parties think very carefully about how many candidates they put up in different constituencies. Transfers often do not take place along party lines, but are often more prominent local personalities benefit. Election posters for the most prominent candidates of a party will typically call it the preferred party of the second preference ( and partly also the third preference).

Voting system criteria

In Scientific analysis of electoral systems such as STV electoral system usually are the criteria to which they meet, in the center. No preference election process meets all the criteria that are described in Arrows impossibility theorem: STV does not satisfy the independence of irrelevant alternatives ( like most other voice-based ranking systems) and not the Monotonizitäts criterion. Failure to comply with the independence of irrelevant alternatives makes STV somewhat vulnerable to strategic nomination, but to a lesser extent as a method by a simple majority, in which the spoiler effect is more pronounced and more predictable.

The non- monotonicity allows, under some circumstances, to choose a preferred candidate by reducing its position on some ballot papers; by helping to choose a candidate who ousted the main opponent of the preferred candidate, a voter can reach sometimes that his preferred candidate of transferred votes profits that come from the defeated enemy.

STV does not meet the participation criterion, which can lead to an STV voters can reach him genehmeres a result by not selected. However, if a candidate is not considered a voter on his ballot in his preference ranking, he harms not considered candidates and helps nobody is not taken into account by him in the rankings to place candidates on the ballot.

STV is also prone to the Alabama paradox: A candidate who has been selected in a given multi- mandate constituency, would not be elected in the same constituency and with the same distribution of votes may, if the electoral district would have one more seat. This is due to the use of quotas; Proportional representation with list selection according to the Hare - Niemeyer method are affected similarly, maximum number of procedures such as the D' Hondt method and Sainte-Laguë/Schepers, however, are not affected.

There are some changes to the STF has been proposed so this satisfies the Monotonizitäts and other criteria. The most common method under the proposed amendments is to change the order, are eliminated in preparing the candidates: A candidate who is on all ballots in second place, it can happen in theory, that it is already eliminated as the first, even if it is Condorcet winner. Meek noted this problem and suggested an amendment in the transfer of votes to eliminate tactical dial STV largely. However, Meek struck even before any method that meets the Condorcet criterion. Other theorists have proposed further refinements of the STV to use a Condorcet method, for example, in determining the elimination order.

Some of these changes alter STV so that it no longer boils when applied to only one to be awarded the seat to instant - runoff voting, but for example, a Condorcet method.

Constituency size

Another question that is often seen in elections with communicable Einzelstimmgebung is the size of the constituency, ie the number of candidates to be elected in the constituency. To a lesser extent, the overall size of the organ to be chosen to play a role. The Transferable Einzelstimmgebung and other proportional representation systems, the number of wasted votes and subsequent rounding error is the less, the greater the number of candidates to be elected. Thus, the distribution of seats in larger constituencies will better meet the preferences of the voters. Therefore, in large constituencies the effects of gerrymandering are substantially reduced; as gerrymandering based on wasted votes for the " last seat " each constituency, to multi-member districts can be difficult to cut in a manipulative way. In some elections with communicable Einzelstimmgebung the constituency size is just three seats, a theoretical upper limit for the district magnitude does not exist in this method. Thomas Hare's original proposal had a single nationwide constituency.

Since the transferable Einzelstimmgebung however is a proportional representation method, requires a candidate in large constituencies only a small share of the vote to be selected. In nine candidate wins each candidate who receives more than 10% of the vote, a seat; with 19 candidates meet 5%.

Larger constituencies and - associated indirectly - a larger number of candidates make it harder for the individual voters to make all candidates in a meaningful ranking. This can lead to an increased number not fully completed ballots and mere orientation to party affiliations.