An electoral district, (election) precinct, election district, or legislative district, called a voting district by the US Census (also known as a constituency, riding, ward, division, electoral area, or electorate) is a territorial subdivision for electing members to a legislative body. Generally, only voters (constituents) who reside within the district are permitted to vote in an election held there. From a single district, a single member or multiple members might be chosen. Members might be chosen by a first-past-the-post system or a proportional representative system, or another voting method entirely. Members might be chosen through a direct election under universal suffrage, an indirect election, or another form of suffrage.
The names for electoral districts vary across countries and, occasionally, for the office being elected. The term constituency is commonly used to refer to an electoral district, especially in British English, but it can also refer to the body of eligible voters or all the residents of the represented area or only those who voted for a certain candidate. The terms (election) precinct and election district are more common in American English. In Australia and New Zealand, electoral districts are called electorates, however elsewhere the term electorate generally refers specifically to the body of voters. In India electoral districts are referred to as "Nirvachan Kshetra" (Hindi: निर्वाचन क्षेत्र) in Hindi, which can be literally translated to English as "electoral area" though the official English translation for the term is "constituency". The term "Nirvachan Kshetra" is used while referring to an electoral district in general irrespective of the legislature. When referring to a particular legislatorial constituency, it is simply referred to as "Kshetra" along with the name of the legislature, in Hindi (e.g.-'Lok Sabha Kshetra' for a Lok Sabha Constituency). Electoral districts for municipal or other local bodies are called "wards". In Canada, districts are colloquially called ridings (stemming from an earlier British geographical subdivision); in French, circonscription or (colloquially) comté, "county." Local electoral districts are sometimes called wards, a term which also designates administrative subdivisions of a municipality. In local government in the Republic of Ireland voting districts are called "electoral areas".
District magnitude is the number of representatives elected from a given district to the same legislative body. A single-member district has one representative, while a multi-member district has more than one. Voting systems that seek proportional representation (such as the single transferable vote) inherently require multi-member districts, and the larger the district magnitude the more proportional a system will tend to be (and the greater the number of distinct parties or choices that can be represented.) Non-proportional systems may use multi-member districts, as in the Unreformed House of Commons, Singapore's Group Representation Constituency, or the New Hampshire House of Representatives.
Under proportional representation systems, district magnitude is an important determinant of the makeup of the elected body. With a larger number of winners, candidates are able to represent proportionately smaller minorities; a 10% minority in a given district may secure no seats in a 5-member election but would be guaranteed a seat in a 9-member one because they fulfill a Droop quota.
The geographic distribution of minorities also affects their representation - an unpopular nationwide minority can still secure a seat if they are concentrated in a particular district. District magnitude can sometimes vary within the same system during an election. In the Republic of Ireland, for instance, national elections to Dáil Éireann are held using a combination of 3, 4, and 5 member districts. In Hong Kong, the magnitude ranged from 3 to 5 in 1998, when the current electoral system was introduced for Legislative Council geographical constituency elections, and will range from 5 to 9 in the forthcoming election in September 2012.
The only democracies with one single nationwide electoral district and no other territorial correctors are Fiji, Israel, The Netherlands, Moldova, Mozambique, Slovakia and South Africa.
Apportionment is the process of allocating a number of representatives to different regions, such as states or provinces. Apportionment changes are often accompanied by redistricting, the redrawing of electoral district boundaries to accommodate the new number of representatives. This redrawing is necessary under single-member district systems, as each new representative requires their own district. Multi-member systems, however, vary depending on other rules. Ireland, for example, redraws its electoral districts after every census while Belgium uses its existing administrative boundaries for electoral districts and instead modifies the number of representatives allotted to each. Israel and the Netherlands avoid the need for apportionment entirely by electing legislators at-large.
Apportionment is generally done on the basis of population. Seats in the United States House of Representatives, for instance, are reapportioned to individual states every 10 years following a census, with some states that have grown in population gaining seats. By contrast, seats in the Cantonal Council of Zürich are reapportioned in every election based on the number of votes cast in each district, which is only made possible by use of multi-member districts, and the House of Peoples of Bosnia and Herzegovina, by contrast, is apportioned without regard to population; the three major ethnic groups - Bosniaks, Serbs, and Croats - each get exactly five members. Malapportionment occurs when voters are under- or over-represented due to variation in district population.
Given the complexity of this process, software is increasingly used to simplify the task, while better supporting reproducible and more justifiable results.
Gerrymandering is the manipulation of electoral district boundaries for political gain. By creating a few "forfeit" districts where opposing candidates win overwhelmingly, gerrymandering politicians can manufacture more, but narrower, wins for themselves and their party. Gerrymandering relies on the wasted-vote effect, effectively concentrating wasted votes among opponents while minimizing wasted votes among supporters. Consequently, gerrymandering is typically done under voting systems using single-member districts, which have more wasted votes.
While much more difficult, gerrymandering can also be done under proportional-voting systems when districts elect very few seats. By making three-member districts in regions where a particular group has a slight majority, for instance, gerrymandering politicians can obtain 2/3 of that district's seats. Similarly, by making four-member districts in regions where the same group has slightly less than a majority, gerrymandering politicians can still secure exactly half of the seats.
However, any possible gerrymandering that theoretically could occur would be much less effective because minority groups can still elect at least one representative if they make up a significant percentage of the population (e.g. 20-25%). Compare this to single-member districts where 40-49% of the voters can be essentially shut out from any representation.
Sometimes, particularly under non-proportional winner-take-all voting systems, electoral districts can be prone to landslide victories. A safe seat is one that is very unlikely to be won by a rival politician due to the makeup of its constituency. Conversely, a swing seat is one that could easily swing either way. In United Kingdom general elections and United States presidential and congressional elections, the voting in a relatively small number of swing seats usually determines the outcome of the entire election. Many politicians aspire to have safe seats. In large multi-party systems like India, swing seats can lead to a Hung assembly like situation if a significant number of seats go for regional parties instead of the larger national parties who are the main competitors at the national or state level, as was the situation in the Lok Sabha (Lower house of The Parliament of India) during the decade of the 1990s.
Elected representatives may spend much of the time serving the needs or demands of individual constituents, meaning either voters or residents of their district. This is more common in assemblies with many single-member or small districts than those with fewer, larger districts. In a looser sense, corporations and other such organizations can be referred to as constituents, if they have a significant presence in an area.
Many assemblies allow free postage (through franking privilege or prepaid envelopes) from a representative to a constituent, and often free telecommunications. Caseworkers may be employed by representatives to assist constituents with problems. Members of the U.S. Congress (both Representatives and Senators) working in Washington, D.C. have a governmentally staffed district office to aid in "constituent services". Many state legislatures have followed suit. Likewise, British MPs use their Parliamentary staffing allowance to appoint staff for "constituency casework". Client politics and pork barrel politics are associated with constituency work.
In some elected assemblies, some or all constituencies may group voters based on some criterion other than, or in addition to, the location they live. Examples include:
Not all democratic political systems use separate districts or other electoral subdivisions to conduct elections. Israel, for instance, conducts parliamentary elections as a single district, while the 26 electoral districts in Italy and the 20 in the Netherlands have a role in the actual election, but no role whatsoever in the division of the seats. Ukraine elected half of the Verkhovna Rada (the Ukrainian Parliament) in this way in the elections in October 2012.