SOCIETY OF AUSTRALIA
DEFINITION: District magnitude is the number of representatives that voters in a particular electoral district are entitled to elect. In systems that use single-member electoral districts, the district magnitude is 1. At the other extreme, with party list systems, in which MPs are not directly elected, as in Israel and the Netherlands - where the whole nation is a single lower house electoral district - the district magnitude can equal the number of MPs in that house.
HARE-CLARK: Proportional representation using the single transferable vote is the only form of PR where the person elected is directly elected by the voters. Therefore the voters have ultimate control over who is elected, as in the Tasmanian and Australian Capital Territory Assemblies, which use the superior Hare-Clark electoral system. In Australia's upper houses, however, political parties' self-serving overlays of stage management and regimented voting arrangements have been imposed, in a fairly effective attempt to reduce that control.
SIZE OF THE DISTRICT MAGNITUDE: The larger the district magnitude becomes, the smaller is the percentage quota required for election, but the larger the expected number of candidates becomes, with a correspondingly large ballot paper, and a large geographical area and number of electors to interact with. New South Wales MLCs are elected from the whole of NSW, but unlike Victoria and Western Australia, whose MLCs do not have a whole state as an electoral district, their office addresses are nearly all in Sydney. A district magnitude should be an odd number from 5 to 9, but it could be just outside that range if a particular case justified it.
AUSTRALIAN FEDERAL PARLIAMENT: Sections 7, 24, and 29 of the Australian Constitution prevent either Senate or House of Representatives electoral districts being formed out of parts of different States, so the largest electoral district in a State for either house cannot exceed the area of the State. Arrangements for coping with that limitation - as Section 128 makes a change most unlikely - have been considered in a PRSA letter to a former Australian Democrats officer. See examples of how electoral districts could be configured for the House of Representatives.
STATE AND TERRITORY LEGISLATURES: These legislatures lack the above constraints on how their electoral districts are arranged. The Tasmanian and ACT Assemblies have never used a district magnitude greater than 7, but the first State Upper Houses to use PR, South Australia and New South Wales, set the whole State as a single electoral district. The later use of PR in Western Australia and Victoria saw much smaller district magnitudes.
MUNICIPAL DISTRICT MAGNITUDES: These vary across Australia, but are always greater than 1, except for urban municipalities in Queensland, and a slowly diminishing minority of municipalities in Victoria.