Paragraph 46(1A)(a) of the Electoral Act specifies:

The reference day is the first day after the end of the 12 month period following for the first meeting day of the House of Representatives.

The first meeting day, also known as the first sitting day, is in Votes and Proceedings, the official record of the proceedings of the House of Representatives.

On the reference day, the Electoral Commissioner is required to ascertain the number of people of:

• the Commonwealth – pursuant to section 45 of the Electoral Act, the number of the people of the Commonwealth does not include the people of the Territories,
• each of the States,
• the Australian Capital Territory, including Jervis Bay,
• the Northern Territory,
• Norfolk Island,
• the Territory of Cocos (Keeling) Islands,
• the Territory of Christmas Island, and
• each of the other Territories – Australian Antarctic Territory, Territory of Heard Island and McDonald Islands, Coral Sea Islands Territory and the Territory of Ashmore and Cartier Islands.

This ascertainment uses statistics supplied by the Australian Statistician.   These statistics must be compiled and published in a regular series under the Census and Statistics Act 1905, with the specific statistics supplied to be those most recently published before the reference day.

The ABS regularly publishes population data.

Calculating how many members of the House of Representatives each state and territory is entitled uses a population quota.

Dividing the ascertained number of people for the Commonwealth by twice the number of Senators for the states gives the population quota.

• Each state has 12 Senators
• The total number of Senators for the states is 72
• Twice the number of Senators for the states is 144

This step applies to New South Wales, Victoria, Queensland, Western Australia, South Australia and Tasmania.

To calculate the number of members of the House of Representatives for a state, the ascertained number of people of the state is divided by the population quota, and the result rounded to the nearest whole number.

Rounding up or down?

In calculating the number of members of the House of Representatives for a state, if the remainder is more than 0.5, the figure for the number of members is rounded up. If the remainder is less than or equal to 0.5, the figure is rounded down (i.e. 32.5 = 32 members, and 32.52 = 33 members).

Tasmania’s entitlement to five members

Section 24 of the Commonwealth of Australia Constitution Act specifies the requirements for the composition of the House of Representatives, requiring that ‘... five members at least shall be chosen in each Original State’. Original States are defined in section 6 as meaning ‘... such States are parts of the Commonwealth at its establishment’.

As Tasmania is an Original State, it is guaranteed a minimum of five members of the House of Representatives.

This step applies to the ACT, the Northern Territory, Christmas Island, Cocos (Keeling) Islands, Norfolk Island, Australian Antarctic Territory, Territory of Heard Island and McDonald Islands, Coral Sea Islands Territory and the Territory of Ashmore and Cartier Islands.

To calculate the number of members of the House of Representatives for a territory, the ascertained number of people of the territory is divided by the population quota, and the result rounded to the nearest whole number.

Rounding up or down?

In calculating the number of members of the House of Representatives for a territory:

• if the result is less than or equal to 0.5 – no member of the House of Representatives will be chosen (i.e. 0.45 = 0 members)
• if the result is greater than 0.5 and less than 1 – one member of the House of Representatives will be chosen (i.e. 0.6 = 1 member)
• if the result is greater than 1 and less than 3 – the number of members to be chosen will be calculated using the harmonic mean:
• 1.3332 = 1 member
• 1.3333 = 2 members
• 2.39 = 2 members
• 2.40 = 3 members
• if the result is 3 or more – if the remainder is more than 0.5, the figure for the number of members is rounded up. If the remainder is less than or equal to 0.5, the figure is rounded down (i.e. 3.5 = 3 members, and 3.52 = 4 members).

Harmonic Mean

The harmonic mean is calculated using the formula:

(2 x Minimum number of members x Minimum number plus 1)
÷
(Minimum number of members + Minimum number plus 1)

Where:

• Minimum of members is the minimum of members worked out for the Territory when dividing the ascertained population by the population quota.
• Minimum number plus 1 is the result of adding 1 to the minimum of members worked out for the Territory when dividing the ascertained population by the population quota.

Minimum number of members for the ACT and Northern Territory

Sub-section 48(2B) of the Electoral Act requires that at least one member of the House of Representatives shall be chosen in the Northern Territory and the ACT at a general election.

• Section 122 of the Commonwealth of Australia Constitution Act allows the Government to make laws for territories and provides that the Government ‘... may allow the representation of such territory in either House of the Parliament to the extent on the terms which it thinks fit’.

When Norfolk Island is not entitled to any members of the House of Representatives, the Electoral Act requires that the population of Norfolk Island is added to that of the ACT and the ACT’s entitlement to members of the House of Representatives is recalculated.

Sub-section 48(2BA) of the Electoral Act provides for the following to occur:

• the ascertainment of the ACT’s population is deemed to have never been made,
• the number of the people of the ACT will be re-ascertained, by adding the number of the people of Norfolk Island to the number of people for the ACT, and
• the Electoral Commissioner will use the newly ascertained number of people of the ACT to determine the number of members of the House of Representatives to be chosen in the ACT.

The territory rounding rules described in Step 5 continue to apply, as does the requirement for a minimum number of members for the ACT.

Under section 56A of the Electoral Act, until such time as the Territory of Cocos (Keeling) Islands or the Territory of Christmas Island is entitled to a member of the House of Representatives, each Territory is to be included in the same electoral division in the Northern Territory.

Sub-section 48(2C) of the Electoral Act provides for the following to occur:

• the ascertainment of the Northern Territory’s population is deemed to have never been made,
• the number of the people of the Northern Territory will be re-ascertained, with the number of people of the Territory of Cocos (Keeling) Islands and the Territory of Christmas Island being added to that of the Northern Territory, and
• the Electoral Commissioner will use the newly ascertained number of people of the Northern Territory to determine the number of members of the House of Representatives to be chosen in the Northern Territory at a general election.

The territory rounding rules described in Step 5 continue to apply, as does the requirement for a minimum number of members for the Northern Territory.

In calculating the number of members of the House of Representatives for the ACT or Northern Territory:

• if the result is greater than 1 and less than 3 – the number of members to be chosen will be calculated using the harmonic mean:
• 1.3332 = 1 member
• 1.3333 = 2 members
• 2.39 = 2 members
• 2.40 = 3 members
• if the result is 3 or more – if the remainder is more than 0.5, the figure for the number of members is rounded up. If the remainder is less than or equal to 0.5, the figure is rounded down (i.e. 3.5 = 3 members, and 3.52 = 4 members).

Harmonic Mean

The harmonic mean is calculated using the formula:

(2 x Minimum number of members x Minimum number plus 1)
÷
(Minimum number of members + Minimum number plus 1)

Where:

• Minimum of members is the minimum of members worked out for the Territory when dividing the ascertained population by the population quota.
• Minimum number plus 1 is the result of adding 1 to the minimum of members worked out for the Territory when dividing the ascertained population by the population quota.

Following ascertainment of the populations and determining the number of members of the House of Representatives for each state and territory, the Electoral Commissioner is required to:

• provide a certificate to the responsible Minister, and
• publish a copy of the certificate in the Gazette within one month of the reference day.

The Minister is required to lay a copy of this certificate before each House of Parliament within five sitting days of receipt of the certificate.

Contents of the certificate

The certificate is required to contain:

• the populations ascertained by the Electoral Commissioner of the Commonwealth, each of the states and each of the territories;
• the number of members of the House of Representatives determined by the Electoral Commissioner;
• any adjustments made to the statistics supplied by the Australian Statistician undertaken in order to ascertain the populations; and
• any calculations or adjustments in determining the number of members of the House of Representatives to be chosen at a general election.

Possible outcomes from the calculating the representation entitlements of states and territories

The possible outcomes from the process are:

• no change to the number of members – no further action is taken;
• change in the number of members – a redistribution of the affected state or territory will be triggered; or
• a territory’s entitlement increases or decreases to one member – the change applies from when the number of members is determined.