The term swing is used in Australia in a different sense from the one employed in the UK

Swing (politics)

An electoral swing analysis shows the extent of change in voter support from one election to another. It is an indicator of voter support for individual candidates or political parties, or voter preference between two or more candidates or parties...

. For the Australian House of Representatives

Australian House of Representatives

The House of Representatives is one of the two houses of the Parliament of Australia; it is the lower house; the upper house is the Senate. Members of Parliament serve for terms of approximately three years....

 and the lower houses of the parliaments of all the Australian states and territories except Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

 and the ACT

Australian Capital Territory

The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory...

), Australia employs preferential voting

Preferential voting

Preferential voting is a type of ballot structure used in several electoral systems in which voters rank candidates in order of relative preference. For example, the voter may select their first choice as '1', their second preference a '2', and so on...

 in single-member constituencies. Under this system, voters number all the candidates on their ballot paper in the order of their preference. Minor candidates are eliminated and their votes are distributed among the remaining candidates according to these preferences.

Thus, in every Australian election using this system, there will be only two candidates remaining at the end of the count. Thus, it is possible to calculate a two-party majority for every seat (also described as the two-party-preferred vote

Two-party-preferred vote

In politics, the two-party-preferred vote , or two-candidate-preferred vote , in an election or opinion poll uses preferential voting to express the electoral result after the distribution of preferences...

). The two-party swing is therefore the swing that will be required for that seat to change hands at the next election.

Example

Here is an example of an election count for a House of Representatives seat, from the 2004 federal election.

First count

It can be seen that the sitting Liberal

Liberal Party of Australia

The Liberal Party of Australia is an Australian political party.Founded a year after the 1943 federal election to replace the United Australia Party, the centre-right Liberal Party typically competes with the centre-left Australian Labor Party for political office...

 member, Trish Worth

Trish Worth

Patricia Mary "Trish" Worth , Australian politician, was a Liberal member of the Australian House of Representatives from March 1993 to October 2004, representing the Division of Adelaide, South Australia...

, had a lead over her Australian Labor Party

Australian Labor Party

The Australian Labor Party is an Australian political party. It has been the governing party of the Commonwealth of Australia since the 2007 federal election. Julia Gillard is the party's federal parliamentary leader and Prime Minister of Australia...

 opponent, Kate Ellis

Kate Ellis

Katherine Margaret "Kate" Ellis, MP is an Australian politician, representing the federal division of Adelaide since 2004 and is currently the Minister for Employment Participation and Childcare and the Minister for the Status of Women in the Gillard Government.-Early life and career:Ellis was...

. In a British election, Worth would have retained the seat, and her majority would be said to be 3.4 percentage points (45.3 minus 41.9). (Note the very high turnout, due to Australia's compulsory voting

Compulsory voting

Compulsory voting is a system in which electors are obliged to vote in elections or attend a polling place on voting day. If an eligible voter does not attend a polling place, he or she may be subject to punitive measures such as fines, community service, or perhaps imprisonment if fines are unpaid...

 laws.)

In this election, however, the votes of all the minor candidates were distributed as follows:

2nd count: Barlow's 978 votes distributed
Party		Candidate	Added votes	%	Votes	%
Liberal}}" |		Trish Worth Trish Worth Patricia Mary "Trish" Worth , Australian politician, was a Liberal member of the Australian House of Representatives from March 1993 to October 2004, representing the Division of Adelaide, South Australia...	172	17.6	38,702	45.5
Democrats}}" |		Richard Pascoe	139	14.2	1,494	1.8
Labor}}" |		Kate Ellis Kate Ellis Katherine Margaret "Kate" Ellis, MP is an Australian politician, representing the federal division of Adelaide since 2004 and is currently the Minister for Employment Participation and Childcare and the Minister for the Status of Women in the Gillard Government.-Early life and career:Ellis was...	206	21.1	35,872	42.2
Greens}}" |		Jake Bugden	365	37.3	7,159	8.4
Family First}}" |		Peter G Robins	96	9.8	1,849	2.2
Total			978		85,076

3rd count: Pascoe's 1,494 votes distributed
Party		Candidate	Added votes	%	Votes	%
Liberal}}" |		Trish Worth Trish Worth Patricia Mary "Trish" Worth , Australian politician, was a Liberal member of the Australian House of Representatives from March 1993 to October 2004, representing the Division of Adelaide, South Australia...	343	23.0	39,045	45.9
Labor}}" |		Kate Ellis Kate Ellis Katherine Margaret "Kate" Ellis, MP is an Australian politician, representing the federal division of Adelaide since 2004 and is currently the Minister for Employment Participation and Childcare and the Minister for the Status of Women in the Gillard Government.-Early life and career:Ellis was...	494	33.1	36,366	42.8
Greens}}" |		Jake Bugden	560	37.5	7,719	9.1
Family First}}" |		Peter G Robins	97	6.5	1,946	2.3
Total			1,494		85,076

4th count: Robins's 1,946 votes distributed
Party		Candidate	Added votes	%	Votes	%
Liberal}}" |		Trish Worth Trish Worth Patricia Mary "Trish" Worth , Australian politician, was a Liberal member of the Australian House of Representatives from March 1993 to October 2004, representing the Division of Adelaide, South Australia...	1,098	56.4	40,143	47.2
Labor}}" |		Kate Ellis Kate Ellis Katherine Margaret "Kate" Ellis, MP is an Australian politician, representing the federal division of Adelaide since 2004 and is currently the Minister for Employment Participation and Childcare and the Minister for the Status of Women in the Gillard Government.-Early life and career:Ellis was...	377	19.4	36,743	43.2
Greens}}" |		Jake Bugden	471	24.2	8,190	9.6
Total			1,946		85,076

5th count: Bugden's 8,190 votes distributed
Party		Candidate	Added votes	%	Votes	%
Liberal}}" |		Trish Worth Trish Worth Patricia Mary "Trish" Worth , Australian politician, was a Liberal member of the Australian House of Representatives from March 1993 to October 2004, representing the Division of Adelaide, South Australia...	1,262	15.4	41,405	48.7
Labor}}" |		Kate Ellis Kate Ellis Katherine Margaret "Kate" Ellis, MP is an Australian politician, representing the federal division of Adelaide since 2004 and is currently the Minister for Employment Participation and Childcare and the Minister for the Status of Women in the Gillard Government.-Early life and career:Ellis was...	6,928	84.6	43.671	51.3
Total			8,190		85,076	1.3

Thus, Ellis defeated Worth, mainly because the great majority of Australian Greens

Australian Greens

The Australian Greens, commonly known as The Greens, is an Australian green political party.The party was formed in 1992; however, its origins can be traced to the early environmental movement in Australia and the formation of the United Tasmania Group , the first Green party in the world, which...

 voters gave their preferences to Labor. Ellis's two-party majority was 1.3 points, and she gained a two-party swing of 1.9 points compared with the previous election. Assuming there is no change of boundaries, the Liberals will require a swing of 1.3 points to regain the seat at the 2007 election.

Thus it can be seen that the concept of "swing" in Australian elections is not simply a function of the difference between the votes of the two leading candidates, as it is in Britain. To know the two-party majority of any seat, and therefore the two-party swing necessary for it to change hands, it is necessary to know the preferences of all the voters, regardless of who they give their first preference votes to. It is not uncommon in Australia for candidates who have comfortable leads on the first count to nevertheless fail to win the seat, because "preference flows" go against them.

The Mackerras Pendulum

Mackerras Pendulum

The Mackerras Pendulum was devised by the Australian psephologist Malcolm Mackerras as a way of predicting the outcome of an election contested between two major parties in a Westminster style lower house legislature such as the Australian House of Representatives, which is composed of...

 takes the two-party majorities of all electorates and arranging them in order, from the seat with the highest government majority to the seat with the highest opposition majority. For example, ahead of the 2007 election, Labor needed to win a minimum of 16 additional seats to form a government, and the 16th weakest government seat (McMillan

Division of McMillan

The Division of McMillan is an Australian Electoral Division in the state of Victoria. It is located in the western part of the Gippsland region, which extends for the length of Victoria's eastern Bass Strait coastline. It includes the outer south-eastern Melbourne suburb of Pakenham, and also...

) had a two-party majority of 4.9 points. Thus the pendulum predicted

Mackerras federal election pendulum, 2006

The Mackerras federal election pendulum, 2006 shows the state of the major political parties ahead of the 2007 Australian federal election. The table shows seats in the Australian House of Representatives arranged in the form of a Mackerras Pendulum based on their 2004 federal election two-party...

 that Labor will need a uniform two-party swing of 4.9 points to win the 2007 election. Labor in fact gained a swing of 5.6 points, which the pendulum had predicted would result in 21 additional Labor seats under a uniform swing. In fact, Labor gained 23 seats, and not all seats that changed hands were the ones with the slimmest Coalition

Coalition (Australia)

The Coalition in Australian politics refers to a group of centre-right parties that has existed in the form of a coalition agreement since 1922...

majorities, because swings in each district are unique and not uniform.