Mackerras Pendulum
Encyclopedia
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 single-member electorates
and which uses a preferential voting
system such as a Condorcet method
or IRV
.
The pendulum works by lining up all of the seats held in Parliament for the government, the opposition and the cross benches according to the percentage point
margin they are held by on a two party preferred basis. This is also known as the swing
required for the seat to change hands. Given a uniform swing to the opposition or government parties, the number of seats that change hands can be predicted.
The two-party preferred (2PP) method of prediction attempts to estimate the flow of second and subsequent preferences from smaller parties in order of their expected elimination during the instant-runoff voting
process, to establish ultimately which major party the voters will choose – Labor or Coalition (Liberal/National) in the Australian context. A Coalition 2PP of 51% would mean a Labor 2PP of 49% and vice versa. Whichever party polls the higher two-party-preferred percentage at the election usually holds the majority of seats to form government. Exceptions to this since 2PP was introduced in 1949
were in 1954
(49.3%), 1961
(49.5%), 1969
(49.8%), 1990 (49.90%), and 1998 (49.02%). 1940
was estimated to have been won on 49.7%.
Mackerras has taken account of fully distributed transferrable preference votes since the 1983 federal election
. Previously, he estimated a two-party-preferred outcome from limited, selective consideration of preferences.
The largest two-party-preferred election result for the Liberal Party of Australia
was at the 1966 federal election
, on 56.9%, while the largest two-party-preferred election result for the Australian Labor Party
was at the 1983 federal election
, on 53.23 percent. The largest unofficial result was 58.2% for Labor at the 1943 federal election
, estimated by Mackerras.
Considering two-party-preferred estimates going back to the 1949 election
, the swing to Labor at the 2007 federal election was the third-largest two-party swing, behind Malcolm Fraser
and the coalition in 1975
on 7.4% and Gough Whitlam
and Labor in 1969
on 7.1%.
Psephology
Psephology is that branch of political science which deals with the study and scientific analysis of elections. Psephology uses historical precinct voting data, public opinion polls, campaign finance information and similar statistical data. The term was coined in the United Kingdom in 1952 by...
Malcolm Mackerras
Malcolm Mackerras
Malcolm Hugh Mackerras AO is an Australian psephologist and commentator and lecturer on Australian and American politics.-Education and works:...
as a way of predicting the outcome of an election contested between two major parties
Two-party system
A two-party system is a system where two major political parties dominate voting in nearly all elections at every level of government and, as a result, all or nearly all elected offices are members of one of the two major parties...
in a Westminster
Westminster System
The Westminster system is a democratic parliamentary system of government modelled after the politics of the United Kingdom. This term comes from the Palace of Westminster, the seat of the Parliament of the United Kingdom....
style lower house
Lower house
A lower house is one of two chambers of a bicameral legislature, the other chamber being the upper house.Despite its official position "below" the upper house, in many legislatures worldwide the lower house has come to wield more power...
legislature
Legislature
A legislature is a kind of deliberative assembly with the power to pass, amend, and repeal laws. The law created by a legislature is called legislation or statutory law. In addition to enacting laws, legislatures usually have exclusive authority to raise or lower taxes and adopt the budget and...
such as 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....
, which is composed of single-member electorates
Single-winner voting systems
A single-member district or single-member constituency is an electoral district that returns one officeholder to a body with multiple members such as a legislature...
and which uses a 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...
system such as a Condorcet method
Condorcet method
A Condorcet method is any single-winner election method that meets the Condorcet criterion, which means the method always selects the Condorcet winner if such a candidate exists. The Condorcet winner is the candidate who would beat each of the other candidates in a run-off election.In modern...
or IRV
Instant-runoff voting
Instant-runoff voting , also known as preferential voting, the alternative vote and ranked choice voting, is a voting system used to elect one winner. Voters rank candidates in order of preference, and their ballots are counted as one vote for their first choice candidate. If a candidate secures a...
.
The pendulum works by lining up all of the seats held in Parliament for the government, the opposition and the cross benches according to the percentage point
Percentage point
Percentage points are the unit for the arithmetic difference of two percentages.Consider the following hypothetical example: in 1980, 40 percent of the population smoked, and in 1990 only 30 percent smoked...
margin they are held by on a two party preferred basis. This is also known as the swing
Swing (Australian politics)
The term swing is used in Australia in a different sense from the one employed in the UK. For the Australian House of Representatives and the lower houses of the parliaments of all the Australian states and territories except Tasmania and the ACT), Australia employs preferential voting in...
required for the seat to change hands. Given a uniform swing to the opposition or government parties, the number of seats that change hands can be predicted.
Two-party-preferred percentage
Instant-runoff voting
Instant-runoff voting , also known as preferential voting, the alternative vote and ranked choice voting, is a voting system used to elect one winner. Voters rank candidates in order of preference, and their ballots are counted as one vote for their first choice candidate. If a candidate secures a...
process, to establish ultimately which major party the voters will choose – Labor or Coalition (Liberal/National) in the Australian context. A Coalition 2PP of 51% would mean a Labor 2PP of 49% and vice versa. Whichever party polls the higher two-party-preferred percentage at the election usually holds the majority of seats to form government. Exceptions to this since 2PP was introduced in 1949
Australian federal election, 1949
Federal elections were held in Australia on 10 December 1949. All 121 seats in the House of Representatives, and 42 of the 60 seats in the Senate were up for election, where the single transferable vote was introduced...
were in 1954
Australian federal election, 1954
Federal elections were held in Australia on 29 May 1954. All 121 seats in the House of Representatives were up for election, no Senate election took place...
(49.3%), 1961
Australian federal election, 1961
Federal elections were held in Australia on 9 December 1961. All 122 seats in the House of Representatives, and 31 of the 60 seats in the Senate were up for election...
(49.5%), 1969
Australian federal election, 1969
Federal elections were held in Australia on 25 October 1969. All 125 seats in the House of Representatives were up for election. The incumbent Liberal Party of Australia led by Prime Minister of Australia John Gorton with coalition partner the Country Party led by John McEwen defeated the Australian...
(49.8%), 1990 (49.90%), and 1998 (49.02%). 1940
Australian federal election, 1940
Federal elections were held in Australia on 21 September 1940. All 74 seats in the House of Representatives, and 19 of the 36 seats in the Senate were up for election...
was estimated to have been won on 49.7%.
Mackerras has taken account of fully distributed transferrable preference votes since the 1983 federal election
Australian federal election, 1983
Federal elections were held in Australia on 5 March 1983. All 125 seats in the House of Representatives, and all 64 seats in the Senate, were up for election, following a double dissolution...
. Previously, he estimated a two-party-preferred outcome from limited, selective consideration of preferences.
The largest two-party-preferred election result for the Liberal Party of Australia
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...
was at the 1966 federal election
Australian federal election, 1966
Federal elections were held in Australia on 26 November 1966. All 124 seats in the House of Representatives were up for election. The incumbent Liberal Party of Australia led by Prime Minister of Australia Harold Holt with coalition partner the Country Party led by John McEwen defeated the...
, on 56.9%, while the largest two-party-preferred election result for the 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...
was at the 1983 federal election
Australian federal election, 1983
Federal elections were held in Australia on 5 March 1983. All 125 seats in the House of Representatives, and all 64 seats in the Senate, were up for election, following a double dissolution...
, on 53.23 percent. The largest unofficial result was 58.2% for Labor at the 1943 federal election
Australian federal election, 1943
Federal elections were held in Australia on 21 August 1943. All 74 seats in the House of Representatives, and 19 of the 36 seats in the Senate were up for election. The incumbent Australian Labor Party led by Prime Minister of Australia John Curtin easily defeated the opposition Country Party led...
, estimated by Mackerras.
Considering two-party-preferred estimates going back to the 1949 election
Australian federal election, 1949
Federal elections were held in Australia on 10 December 1949. All 121 seats in the House of Representatives, and 42 of the 60 seats in the Senate were up for election, where the single transferable vote was introduced...
, the swing to Labor at the 2007 federal election was the third-largest two-party swing, behind Malcolm Fraser
Malcolm Fraser
John Malcolm Fraser AC, CH, GCL, PC is a former Australian Liberal Party politician who was the 22nd Prime Minister of Australia. He came to power in the 1975 election following the dismissal of the Whitlam Labor government, in which he played a key role...
and the coalition in 1975
Australian federal election, 1975
Federal elections were held in Australia on 13 December 1975. All 127 seats in the House of Representatives, and all 64 seats in the Senate were up for election following a double dissolution of both Houses....
on 7.4% and Gough Whitlam
Gough Whitlam
Edward Gough Whitlam, AC, QC , known as Gough Whitlam , served as the 21st Prime Minister of Australia. Whitlam led the Australian Labor Party to power at the 1972 election and retained government at the 1974 election, before being dismissed by Governor-General Sir John Kerr at the climax of the...
and Labor in 1969
Australian federal election, 1969
Federal elections were held in Australia on 25 October 1969. All 125 seats in the House of Representatives were up for election. The incumbent Liberal Party of Australia led by Prime Minister of Australia John Gorton with coalition partner the Country Party led by John McEwen defeated the Australian...
on 7.1%.
See also
- Mackerras federal election pendulum, 2006Mackerras federal election pendulum, 2006The 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...
- Post-election pendulum for the 2007 Australian federal election
- Post-election pendulum for the Australian federal election, 2010
- Pre-election pendulum for the next Australian federal electionPre-election pendulum for the next Australian federal electionThe following pendulum is known as the Mackerras Pendulum, invented by psephologist Malcolm Mackerras. Designed for the outcome of the 2010 federal election and changes since, the pendulum works by lining up all of the seats held in Parliament, 72 Labor, 71 Coalition, 1 Nationals WA, 1 Green and 5...
- SwingometerSwingometerThe swingometer is a graphics device that shows the swing from one party to another on British election results programmes. It was invented by Peter Milne, and later refined by David Butler and Robert McKenzie....
, a graphical device with similar functionality used in the United Kingdom since 1955