Latest release

Household and Family Projections, Australia methodology

Reference period
2016 - 2041
Released
14/03/2019
Next release Unknown
First release

Explanatory notes

Introduction

1 This publication contains 2016-based projections of households, families and living arrangements for the period 2016 to 2041. The projections are available for Australia, states and territories, capital cities and rest of states. These projections supersede the 2011-based series published in Household and Family Projections, Australia, 2011 to 2036 (cat. no. 3236.0) in March 2015.

Geography definition

2 Capital cities and rest of states are the GCCSA level of the Australian Statistical Geography Standard (ASGS) 2016 (cat. no. 1270.0.55.001). The ASGS defines the whole ACT as a capital city area, thus projections were not produced below the Territory level for the ACT. The projections for Australia include Christmas Island, Cocos (Keeling) Islands, Jervis Bay Territory and Norfolk Island, collectively referred to as Other Territories.

Household definition

3 A household is defined as one or more persons, at least one of whom is at least 15 years of age, usually resident in the same private dwelling. Although in reality some living arrangements are fluid, the Census assigns each person to a single household. The projection method therefore treats households as discrete units.

Method

4 These projections use a propensity method based on that developed by McDonald and Kippen and used in Household Trends and Projections: Victoria, 1986-2011. The method identifies propensities from the Census of Population and Housing for persons to be in different living arrangements. Trends observed in the propensities over the last four Censuses are assumed to continue into the future, and applied to a projected population. Numbers of families are then derived from the projected living arrangements of the population, and numbers of households are derived from the projected numbers of families. For details see Technical Note - 'Method'.

Background

5 The projection results are not predictions or forecasts. They are illustrations of the change in the numbers of households and families that would occur if assumptions about future trends in living arrangements were to occur.

6 The assumptions are based on past trends in living arrangements. No assessment has been made of changes in social and economic conditions which may influence future living arrangements. There is no certainty that any of the assumptions will be realised.

Sources of data

7 Sources of data for the projections are:

• The 2001, 2006, 2011 and 2016 Censuses of Population and Housing
• Estimated resident population at 30 June 2016 and 30 June 2017
• Estimated households at 30 June 2016
• ABS population projections at 30 June 2018 to 2041

Census of population and housing

8 Three Census items are used to obtain living arrangement propensities. These are household composition, family composition, and relationship in household of the usual resident population.

9 The Census only collects information on the relationship of each household member to person 1 and/or person 2 on the Census form. Relationships between other members of the household (e.g. between person 3 and person 4) are not captured. This may lead to an underestimation of the number of families, as well as relationships within the household and family type.

10 Person-level ‘relationship in household’ data within the Census is based on place of enumeration. This means persons temporarily absent from the household were excluded from the propensities due to limited relationship information. Visitors to households on Census night were also excluded from the propensities because they are not included in family coding in the Census.

Estimated Resident Population

11 Estimated Resident Population (ERP) published in Australian Demographic Statistics (cat. no. 3101.0) is used as the 2016 and 2017 population base (projected population is used for later years).

12 ERP is based on Census counts of usual residents, with adjustments made for Census undercount (people present in Australia on Census night but missed by the Census count) and usual residents of Australia who were temporarily overseas at the time of the Census.

13 ERP does not distinguish between people who live in private versus non-private dwellings (NPDs). Household and family projections are concerned exclusively with the population usually resident in private dwellings. Therefore, for the purposes of these projections, the proportion of the Census count in NPDs was identified and excluded from the calculation of numbers of households and families. People living in NPDs are included in the analysis of living arrangements.

Estimated households

14 Estimated households are used to constrain the base year (2016) living arrangement propensities calculated from the 2016 Census. For details see Technical Note - 'Method'.

15 The 2016 estimated households in Australia in this publication (9,204,635) is greater than the 2016 Census count of households (8,286,077) published in various 2016 Census publications. The difference is a combination of dwelling undercount and dwelling misclassification in the Census and persons that were temporarily overseas on Census night. For the differences between Census counts and ERP see Explanatory Notes 11 to 13.

Populations projections

16 Projected number of persons reflect the Series B population projections published in Population Projections, Australia, 2017 (base) - 2066 (cat. no. 3222.0)

17 Series B assumes ‘medium’ levels of future births, deaths and migration, based recent historical trends:

• the total fertility rate for Australia declining to 1.8 babies per woman in 2027, and remaining constant thereafter;
• life expectancy at birth will reach 82.1 years for males and 85.5 years for females by 2041;
• net overseas migration will reach 225,000 people per year by 2027 and remain constant thereafter;
• net interstate migration gains for some states and territories, and losses for others.

18 Only one population projection series is used. This means that the differences between the three series of household, family and living arrangement projections only reflect the different living arrangement assumptions, rather than differences in the underlying population.

19 Chapter 9 – ‘What If . . .’ discusses the results of using two other projections of the population, the Series A and Series C projections from Population Projections, Australia, 2017 (base) - 2066 (cat. no. 3222.0), as the assumptions about the future population of Australia and the states and territories.

Rounding

21 Usually, in this publication, figures of less than one million are rounded in the text to the nearest hundred while figures of more than one million are rounded to the nearest hundred thousand.

Percentage growth

22 Changes in population over time are commonly discussed in terms of average annual growth rates. In this publication, however, changes are for the most part presented as percentage increases or decreases over the entire 25-year period (from 2016 to 2041), in order to make differences between projected numbers (of households, families and people in different living arrangements) more discernible.

Comparison with state government household projections

23 Some state and territory governments produce household projections, which may be a useful complement to the projections in this publication. These are typically based on different methods and are produced with specific attention to the observed and expected trends of that state, without the requirement of being constrained to Australia level data.

Acknowledgment

24 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act 1905.

25 As well as the statistics included in this and related publications, the ABS may have other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070.

Technical note - method

Introduction

1 These projections use a propensity method based on that developed by McDonald and Kippen and used in Household Trends and Projections: Victoria, 1986-2011. The method identifies propensities from the Census of Population and Housing for persons to be in different living arrangements. Trends observed in the propensities over the last four Censuses are assumed to continue into the future, and applied to a projected population. Numbers of families are then derived from the projected living arrangements of the population, and numbers of households are derived from the projected numbers of families.

Method

2 The method for obtaining household and family projections is outlined below. The method consists of five main steps:

• Step 1: Calculate living arrangement propensities from Census
• Step 2: Calculate assumed future living arrangement propensities based on past trends
• Step 3: Derive projected living arrangements from assumed future propensities
• Step 4: Derive projected numbers of families from the projected living arrangements
• Step 5: Derive projected numbers of households

Step 1: Calculate living arrangement propensities from census

3 2016 living arrangement propensities were calculated for each five-year age group (0–4, 5–9, …, 85 and over). The propensity is the Census counts of people (for each age group) in that living arrangement type, divided by the total Census count for each age group. There are 15 living arrangement types, as shown in summary tables in the page 'Types of Living Arrangements'.

4 Living arrangement propensities were calculated using a large proportion (91% in 2016) of the Census count of Australian usual residents. Categories of people included in the 2016 Census counts but excluded from the calculation of living arrangement propensities were:

• imputed records.
• people coded to 'other non-classifiable' relationship in household.
• visitors in the private dwelling in which they were enumerated, who were usually resident elsewhere in Australia.
• people enumerated in non-private dwellings who were usually resident elsewhere in Australia.

5 People included in the projected population but not included in the living arrangement calculation were proportionally distributed across the living arrangement types. This assumes that these people have the same living arrangement distribution as those included in the calculation of the propensities.

6 Distributing by this method is likely to lead to an underestimation of lone-person households. It is less likely that a lone-person household will be enumerated at home on Census night because there are fewer people in the household. This bias is addressed in part by replacing Census counts of lone-person households with lone-person household estimates in the propensity calculations.

7 Census-based living arrangement propensities in the base year (2016) are reconciled to align with the estimate of households published in Australian Demographic Statistics (cat. no. 3101.0) for both total households and lone-person households. These estimates are based on Census counts but have been adjusted to account for person and dwelling undercount, dwelling misclassification and residents temporarily overseas on Census night.

8 The difference between the total numbers of households and lone-person households was proportionally distributed to group and family households. The number of families and then persons by living arrangement were derived from the scaled household estimates, using the method outlined in step 4 (paragraphs 17 to 18) in reverse. For example, to obtain the number of persons in a group household, the ‘reconciled’ number of group households was multiplied by the average size of group households in the 2016 Census.

9 The 2016 reconciled counts by living arrangement were proportionally distributed across the five-year age groups according to the 2016 living arrangement propensities (as described in paragraph 3). The distribution was constrained to sum to 30 June 2016 ERP (by age) and the reconciled totals for each living arrangement.

10 Reconciled base year living arrangement propensities are used in step 2 as the basis for the projected propensities.

Step 2: Calculating assumed future living arrangement propensities

11 A line of best fit was calculated for each living arrangement (for each age group), using the observed 2001, 2006, 2011 and 2016 propensities. If the fitted straight line produced an r-squared value of less than 0.2, it was assumed there had been no change in propensity between 2001 and 2016, and therefore the 2016 propensity for that living arrangement for that age group was held constant throughout the projection period in all three assumption series. The annual rate of change for each line of best fit was calculated.

12 Assumed rates of change were applied to the 2016 reconciled propensities to give projected propensities for the period 2017 to 2041 for each living arrangement (for each age group). This produced three series of projected propensities. Series I holds 2016 propensities constant over the whole period, series II assumed the observed trend would continue at a decreasing rate, and series III continues at the full rate of change over the whole projection period. For more information see the page 'Assumptions'.

13 Projected propensities were adjusted to ensure they sum to 100% in each five-year age group using iterative proportional fitting.

Step 3: Derive projected persons by living arrangement from assumed future propensities

14 The projected propensities were then applied to the projected population of each age group to produce the projected number of people in each living arrangement, for each year from 2017 to 2041.

15 Propensities were produced independently for Australia, the states, territories, capital cities and each balance of state. They were then applied to the relevant projected population.

16 State-level data was constrained to sum to the Australian living arrangement totals and five-year age group totals. This was done using two-dimensional iterative proportional fitting. The process was then repeated to constrain capital city and rest of state data to state data. For a more detailed description of iterative proportional fitting, see Purcell, N. J. and Kish, L., (1979), Estimations for small domains, Biometrics, 35, pp. 365-384.

Step 4: Derive projected number of families from living arrangement projections

17 The number of couple families (with or without children) was calculated as half the number of partners in couple families (with or without children). The number of one-parent families was calculated as the number of male lone parents plus the number of female lone parents. The number of 'other families' was calculated by dividing the number of persons living in 'other families' by the average size of 'other families' at the 2016 Census. See paragraph 22 for the average size of ‘other families’ by part of state.

18 The 2016 estimate of the number of families in Australia in this publication (6,659,038) is greater than the 2016 Census count of families (6,070,316) published in various 2016 Census publications. The difference is a combination of net undercount in the Census and families that were temporarily overseas on Census night. For the differences between Census counts and ERP see Explanatory Notes 11 to 13.

Family households

19 Family households can contain more than one family. The number of family households was calculated as the number of families multiplied by the ratio in the 2016 Census of family households to families – see paragraph 22 for ratios by part of state.

Non family households

20 The number of lone-person households was calculated as the number of male lone persons plus the number of female lone persons. The number of group households was calculated by dividing the number of persons in group households by the average size of group households at the 2016 Census. See paragraph 22 for average group household size by part of state.

Total households

21 Total projected households is the sum of all household types.

Census ratios

22 The ratios mentioned in paragraphs 17, 19 and 20 above are presented in the following table:

2016 Census ratios
Average size of 'other families' (a) (people)Family households to families ratio (b) (people)Average size of group households (c) (people)
Sydney2.150.962.45
Rest of NSW2.080.982.17
Melbourne2.120.972.41
Rest of Vic.2.070.992.21
Brisbane2.110.972.35
Rest of Qld2.100.982.15
Rest of SA2.120.992.10
Perth2.120.982.29
Rest of WA2.180.982.11
Greater Hobart2.090.992.28
Rest of Tas.2.070.992.10
Darwin2.170.972.27
Rest of NT2.610.842.25
ACT2.090.982.37
1. The number of people living in 'other families', divided by the number of 'other families'
2. The number of family households, divided by the number of families
3. The number of people living in group households, divided by the number of group households.

Geographical areas

23 The propensities were derived using the area boundaries according to the relevant ABS Geography classification of each capital city and rest of state area as they existed at the relevant reference points (2001, 2006, 2011 and 2016). Previous analysis suggests that the use of such propensities (rather than based on revised areas) would not have had a significant effect on the comparability of the propensities over time.

Glossary

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Average annual growth rate

The average annual growth rate, r, is calculated as a percentage using the formula:

$$\large{r=\left[\left(\frac{P_{n}}{P_{0}}\right)^{\frac{1}{n}}-1\right] \times 100}$$

where $${P_0}$$ is the population at the start of the period, $${P_n}$$ is the population at the end of the period and n is the length of the period between $${P_n}$$ and $${P_0}$$ in years.

Average household size

Average household size refers to the number of persons per household in private dwellings.

Capital city

Refers to the Greater Capital City Statistical Areas of states and territories as defined in the Australian Statistical Geography Standard.

Child

A child is a person of any age who is a natural, adopted, step or foster son or daughter of a couple or lone parent, usually resident in the same household. A child is also any individual under 15 years, usually resident in the household, who forms a parent-child relationship with another member of the household. This includes otherwise related children under 15 years and unrelated children under 15 years.

In order to be classified as a child, the persons can have no partner or child of his/her own usually resident in the household. A separate family in the household is formed in this instance. If a person is aged under 15 years and has a partner/spouse these relationships are not recorded.

Couple family with children

A family based on two persons who are in a registered or de facto marriage, who are usually resident in the same household. The family must include one or more children usually resident in the same household. The family may include any number of other related individuals usually resident in the household.

Couple family without children

A family based on two persons who are in a registered or de facto marriage, who are usually resident in the same household and have no children usually resident in the same household. The family may include any number of other related individuals usually resident in the household.

Dwelling

A dwelling is a building or structure in which people live. Some examples of dwellings are a house, a block of flats, a caravan or tent, prison, humpy or houseboat. For the purposes of Census of Population and Housing, dwellings are classified into private and non-private dwellings. Each of these dwelling types is further divided into occupied and unoccupied dwelling categories.

Estimated households

Estimated households is a measure of the number of households, which corresponds to the usual resident population living in private dwellings. It is based on the Census count of households and adjusted to account for dwelling undercount, dwelling misclassification, residents counted away from home on Census night and residents temporarily overseas on Census night. It excludes groups of visitors (from overseas or elsewhere in Australia) counted by Census in the same dwelling, as they do not form a household.

Estimated resident population

The official measure of the population of Australia is based on the concept of usual residence. It refers to all people, regardless of nationality or citizenship, who usually live in Australia, with the exception of foreign diplomatic personnel and their families. It includes usual residents who are overseas for less than 12 months over a 16-month period. It excludes overseas visitors who are in Australia for less than 12 months over a 16-month period.

Estimates of the Australian resident population are generated on a quarterly basis by adding natural increase (births minus deaths) and net overseas migration (NOM) occurring during the period to the population at the beginning of each period. This is known as the cohort component method, and can be represented by the following equation:

P$$_{t+1}$$ = P$$_t$$ + B - D + NOM, where:

P$$_t$$ = the estimated resident population at time point $$t$$

P$$_{t+1}$$ = the estimated resident population at time point $$_{t+1}$$

B = the number of births occurring between $$t$$ and $$_{t+1}$$

D = the number of deaths occurring between $$t$$ and $$_{t+1}$$

NOM = net overseas migration occurring between $$t$$ and $$_{t+1}$$.

For state and territory population estimates, an additional term is added to the equation representing net interstate migration (NIM) occurring between $$t$$ and $$t+1$$, represented by the following equation:

P$$_{t+1}$$ = P$$_t$$ + B - D + NOM + NIM.

Family

A family is defined by the ABS as two or more persons, one of whom is at least 15 years of age, who are related by blood, marriage (registered or de facto), adoption, step or fostering, and who are usually resident in the same household. The basis of a family is formed by identifying the presence of either a couple relationship, lone parent-child relationship or other blood relationship. Some households will contain more than one family.

Family composition

A classification of families based on the presence, or absence, of a couple relationship, parent-child relationship, or other blood relationship.

Family growth

Growth in the number of families.

Group household

A group household is a household consisting of two or more unrelated people where all persons are aged 15 years or over. There are no reported couple relationships, parent-child relationships or other blood relationships in these households.

Household

A household is defined as one or more persons, at least one of whom is at least 15 years of age, usually resident in the same private dwelling.

Persons usually resident in non-private dwellings, such as hotels, motels, boarding houses, gaols and hospitals, are not included in household estimates.

This definition of a household is consistent with that used in the Census.

Household composition

Household composition is used to describe and categorise households on the basis of the number of families present, and whether or not unrelated household members are present (if it is a family household), or the number of household members (if it is a non-family household).

Household count

The count of households is the number of households counted in the Census. It is not adjusted for undercount, dwellings containing overseas visitors, households of Australian residents where all members were temporarily overseas at the time of the Census, households of Australian residents where all members were not home on Census night and spent Census night in a non-private dwelling in Australia, and households of Australian residents where some members were not at home on Census night and were counted as a separate household elsewhere. Characteristics of households are available according to place of enumeration.

Household growth

Growth in the number of households.

Household population

The household population is the estimated resident population (ERP) that usually lives in private dwellings. It is the ERP less the population that usually lives in non-private dwellings.

Life expectancy

Life expectancy refers to the average number of additional years a person of a given age and sex might expect to live if the age-specific death rates of the given period continued throughout his or her lifetime.

Living arrangement

Living arrangement combines the three concepts 'relationship in household', 'family type' and 'household type'. It is used to describe the familial and non-familial relationship type of each person, within each family type, and within each household type.

Lone parent

A person who has no spouse or partner present in the household but who forms a parent-child relationship with at least one child usually resident in the household.

Lone person

A person at least 15 years of age who lives in a dwelling on their own.

Non-private dwelling (NPD)

Non-private dwellings (NPDs) are residential dwellings with accommodation which are not included in the Census of Population and Housing list of private dwelling categories. NPDs are classified according to their function. They include hotels, motels, guest houses, prisons, religious and charitable institutions, military establishments, hospitals and other communal dwellings. Where this type of accommodation includes self-contained units (as provided by hotels, motels, homes for the elderly and guest houses), the units are enumerated as part of the NPD. Complexes such as retirement villages, which have a combination of self-contained units, hostel and/or nursing home accommodation, are enumerated as NPDs.

Occupied private dwelling

An occupied private dwelling is defined as the premises occupied by a household on Census night.

One-parent family

A family consisting of a lone parent with at least one child (regardless of age) who is also usually resident in the household. The family may also include other related individuals.

Other family

A family of related individuals residing in the same household. These individuals do not form a couple or parent-child relationship with any other person in the household and are not attached to a couple or one-parent family in the household. For example, a household consisting of a brother and sister only.

Other related individual

An individual who is related to at least one other member of the household, but who does not form a couple or parent-child relationship.

Partner

A person in a couple relationship with another person usually resident in the same household. The couple relationship may be in either a registered or de facto marriage, and includes same-sex couples.

Private dwelling

A private dwelling (PD) in the Census is defined as a house, flat, part of a house, or even a room; but can also be a house attached to, or rooms above shops or offices; an occupied caravan in a caravan park or boat in a marina, a houseboat, or its own block of land. A caravan situated on a residential allotment is also classed as a PD.

Relationship in household

Describes the familial and non-familial relationship of each person within each family in a given household. The familial relationship within each family is measured with reference to a family reference person chosen for that particular family.

Residents temporarily overseas

Residents temporarily overseas are Australian residents who are overseas for a period less than 12 months.

Rest of state or territory

Within each state and territory, except for the ACT, the area not defined as being part of the Greater Capital City Statistical Area is call the Rest of State region.

Total fertility rate

The sum of age-specific fertility rates (live births at each age of mother per female population at that age). It represents the number of children a female would bear during her lifetime if she experienced current age-specific fertility rates at each age of her reproductive life.

Unoccupied private dwellings

These are structures built specifically for living purposes which are habitable, but unoccupied at the time of the Census of Population and Housing. Vacant houses, holiday homes, huts, cabins (other than seasonal workers' quarters) and houseboats are counted as unoccupied dwellings. Also included are newly completed dwellings not yet occupied, dwellings which are vacant because they are due for demolition or repair, dwellings to let and dwellings where all members of the household were absent on Census night.

Usual residence

Usual residence within Australia refers to that address at which the person has lived or intends to live for a total of six months or more in a given reference year.

Quality declaration - summary

Institutional environment

The Australian Bureau of Statistics (ABS) household and family projections are produced from a combination of ABS data: the 5-yearly Census of Population and Housing, estimated resident population, household estimates and population projections.

For information on the institutional environment of the ABS, including the legislative obligations of the ABS, financing and governance arrangements, and mechanisms for scrutiny of ABS operations, please see ABS Institutional Environment.

Relevance

Household and family projections inform on future changes in numbers and types of households and families, and are used in a variety of planning decisions. Projections are published for Australia, the states, territories, capital cities and rest of state regions.

Timeliness

ABS household and family projections are compiled and published once every five years; typically, three years following the most recent ABS Census of Population and Housing.

Accuracy

ABS household and family projections are based on assumptions about future living arrangements of Australia's population. They are not intended as predictions or forecasts, but are illustrations of growth and change in numbers and types of households and families that would occur if assumptions about future living arrangements of Australia's population were to prevail over the projection period.

While the assumptions are formulated on the basis of an assessment of demographic trends, there is no certainty that any of the assumptions will be realised. In addition, no assessment has been made of possible future changes in non-demographic conditions.

It is important to also recognise that the future population of Australia underlying the household and family projections is itself based on a range of assumptions (about future fertility rates, mortality rates and levels of migration). For the purpose of this publication, the Series B projection from Population Projections, Australia, 2017 (base) - 2066 (cat. no. 3222.0) has been used as Australia's future population.

Coherence

As the assumptions used in each successive set of household and family projections incorporate recent trends, comparison of data across issues of this publication is not possible. However, projected numbers of households are compatible and comparable with ABS household estimates for 2016 and earlier years.

Estimates of the number of families in 2016 in this publication differ from counts of families from the 2016 Census of Population and Housing. This is due to estimates of families in this publication being based on 2016 estimated resident population as well as 2016 Census living arrangement propensities. The 2016 estimated resident population of Australia is greater than the 2016 Census count of people in Australia as it includes Census net undercount and residents temporarily overseas, and as a result, the number of families based on 2016 estimated resident population is greater than the number of families from the 2016 Census.

Interpretability

ABS household and family projections are not intended as predictions or forecasts, and should not be considered as such. Rather, they are illustrations of growth and change in numbers of households and families in Australia that would occur if the assumptions were to prevail over the projection period. As future trends in living arrangements are unpredictable, three assumptions have been made regarding these, to illustrate a range of possible future outcomes.

This publication contains notes on the assumptions and methods used to produce the household and family projections. It also contains Explanatory Notes, Appendices and a Glossary that provide information on the data sources, terminology, classifications and other technical aspects associated with these statistics.

Accessibility

ABS household and family projections are available in a variety of formats on the ABS website under the 3236.0 product family. The formats available are:

• Main Features, which contains key figures commentary;
• three data cubes (in Microsoft Excel format) containing numbers of households, families, and persons by living arrangement for Australia, the states, territories, capital cities and rest of state regions, for 2016 to 2041;
• one data cube (in Microsoft Excel format) containing living arrangement propensities for Australia for the 2001 to 2016 Censuses; and
• three ABS.Stat datasets containing numbers of households, families, and persons by living arrangement for Australia, the states, territories, capital cities and rest of state regions, for 2016 to 2041.

If the information you require is not available as a standard product, then ABS Consultancy Services can help you with customised services to suit your needs. For inquiries contact the National Information and Referral Service on 1300 135 070 or email client.services@abs.gov.au.

The ABS observes strict confidentiality protocols as required by the Census and Statistics Act, 1905. This may limit access to data at a detailed level.

Abbreviations

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 ABS Australian Bureau of Statistics ACT Australian Capital Territory ASGS Australian Statistical Geography Standard Aust. Australia Bal Balance ERP Estimated Resident Population GCCSA Greater Capital City Statistical Area no. number NPD Non-Private dwelling NSW New South Wales NT Northern Territory Qld Queensland SA South Australia Tas. Tasmania Vic. Victoria WA Western Australia