Each district should return an odd number of members (i.e. the district magnitude should be odd, such as 5 or 7) because it ensures that an absolute majority of votes for a given grouping of candidates – however slight – produces an absolute majority of seats for that grouping.
In contrast, with an even number of members (such as 4 or 6), an absolute majority of votes for a grouping does not, unless it is high enough, produce an absolute majority of seats for that grouping.
For example, if 4-member districts were used there is a strong chance that each district will return 2 each from the major parties, thus not providing any indication if the electorate had swung slightly in one direction or the other. In contrast, with 5-member districts, a small majority to one party will result in that party winning 3 while the other party only wins 2.
Apart from better reflecting the view of the district, this design also results in more districts becoming marginal, where the last seat can easily swing between parties or to an independent.
Discussion on thestalemate problem appeared as far back as 1912, in Section 6 of Tasmania’s Report on the 1912 General Election.
A 1958 report to the Parliament of Tasmania on the defects of the original 6-member electoral districts used in Tasmania’s Hare-Clark system recommended that they be changed to an odd number (7). This did occur, prior the districts being changed to 5-member districts for the 1998 elections.
Entrenching an odd-number
Examples of entrenchment to avoid an even number of places are:
- Section 4 (1) (a) of the Proportional Representation (Hare-Clark) Entrenchment Act 1994 of the Australian Capital Territory entrenches the requirement that an odd number of members of the Legislative Assembly shall be elected from each electorate, and
- Section 16.2.5 of the Constitution of the Republic of Ireland requires the use of the system of proportional representation using the single transferable vote, and Section 16.2.6 requires that no constituency shall elect fewer than three members, which at least avoids the worst case of an odd number, where only 2 members are to be elected.
Each electoral district should return an odd number of members.