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Executive summary
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This Research Paper shows the notional two-party preferred swing needed for each electoral division (seat) to change hands at the next House of Representatives election. The two-party preferred votes are the results of the 2004 election adjusted for the effects of electoral redistributions which occurred in the Australian Capital Territory (ACT) during 2005, and New South Wales (NSW) and Queensland during 2006.
The redistribution in the ACT was triggered by the passage of time—a redistribution must be held in each state and territory at least every seven years. There was no change in the number of divisions resulting from this redistribution.
The NSW and Queensland redistributions were triggered
by a change in the two States’ entitlements to representation in the
House of Representatives in the 2005 determination by the Australian
Electoral Commissioner. The redistributions resulted in the creation
of a new division,
The 2005 redistribution in the ACT did not change the
notional party status of either of the two divisions. Both the divisions
of Canberra and
The 2006 redistributions resulted in NSW losing a seat
[2]—the northern, rural
seat of Gwydir safely held by the Coalition—reducing its entitlement
to 49 divisions, while Queensland increased its entitlement to 29 seats
with the creation of
Only two seats changed their notional party status
because of the redistributions; both in NSW. The inner metropolitan
The above outcomes result in a notional composition of the House of Representatives before the next election of 87 Coalition members, 60 Labor and 3 Independents for a total of 150 members: unchanged from the actual position after the 2004 election. This gives the Coalition a majority of 24 seats in the lower house. The Coalition would lose its absolute majority if (net) 12 seats were lost at the next election. However, because of the three Independent members, Labor would need to win an additional (net) 16 seats to be able to form government in its own right.
A further issue to consider is the situation in the
independently held divisions of Calare and New England in NSW and
Calare, however, was substantially redrawn: 45 per cent of its voters were transferred to the seat of Macquarie. In addition, its area was increased from 21 621 to 237 325 square kilometres by taking in a large part of ‘old’ Parkes to the Queensland border.
With the independent member for Calare,
the effective abolition of the seat of Calare with its splitting into two ... made that decision easier; [6]
it is feasible to suggest that Calare is now notionally a Coalition seat—on a two-party preferred basis, Calare is a safe Coalition seat with a margin of 11.1 per cent.
Under this assumption, the notional composition of the House of Representatives leading into the next election is 88 Coalition members, 60 Labor and 2 Independents. This means the Coalition would need to lose (net) 13 seats to lose its absolute majority at the next election. The Labor party still needs to win an additional (net) 16 seats to be able to win government.
The Appendix gives a table (commonly known as a pendulum) of the two-party preferred margin (or swing) required to lose each seat at the next election. [7] The seats are grouped in LP/NP (Coalition), ALP (Labor) and Independent seats. Within the party groupings, the seats are ranked from highest to lowest margin.
Based on the pendulum the ALP requires a ‘uniform’ two-party preferred swing of just over 4.8 per cent to gain the necessary 16 seats to win government at the next election.
However, it is worth remembering that the pendulum
is not always an accurate predictor of which seats may be lost and won
because election swings are not necessarily uniform across
The 2005 and 2006 redistributions in the ACT, NSW and Queensland have maintained a House of Representatives of 150 seats for the next election, although NSW lost a seat and Queensland gained one.
The reworking of the 2004 election results onto the new electorate boundaries, however, has not resulted in a notional composition change between the parties in the House of Representatives since the 2004 election; although, the major redrawing of the boundaries of Calare may notionally have resulted in an additional seat for the Coalition.

[1]. A ‘marginal’ seat (electoral division) has a two-party preferred margin of less than 6 per cent; ‘fairly safe’ is 6 per cent to 10 per cent; and a ‘safe’ seat above 10 per cent. http://www.aec.gov.au/About_AEC/Publications/Newsfiles/2005/No_124.htm#20%20most%20marginal, accessed 28 August 2007.
[2]. For further
discussion regarding this, see
[3]. Named in honour of the Reverend John Flynn, founder of the Royal Flying Doctor Service, Flynn stretches in a westward band from the port of Gladstone to Winton.
[4].
New England lost no voters to other divisions and gained a small number
of voters from the abolished Gwydir. These new voters amount to only
about four per cent of the total voters of the new electorate.
[5].
At the 2004 election,
[6].
[7]. The margins shown in the pendulum are as estimated by the Australian Electoral Commission (AEC). Individual margins may vary very slightly from the Parliamentary Library’s estimated pendulum provided to Senators and Members on the Library’s intranet from late last year. The AEC’s margins are shown because they will be used to calculate the swings at the next election. Source: AEC, National Seat Status—including notional seat status for the Australian Capital Territory, New South Wales and Queensland, Electoral Newsfile No. 131 July 2007, accessed 28 August 2007.
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