Census of Population and Housing - Counts of Aboriginal and Torres Strait Islander Australians methodology

This publication presents counts from the 2016 Census of Population and Housing for people who identified as being of Aboriginal and/ or Torres Strait Islander origin and were counted in the 2016 Census of Population and Housing.

The 2016 Census of Population and Housing was held on 9 August 2016. The Census is the largest statistical collection undertaken by the Australian Bureau of Statistics. By counting the number and key characteristics of people in Australia on Census Night, the Census provides a reliable basis for the estimation of the population of the states, territories and local government areas, for use in:

• determining the number of seats allocated to each state in the House of Representatives
• distributing billions of dollars of annual goods and services tax revenue to the states and territories
• determining state grants to local government areas.
   

As well as key demographic characteristics such as age and sex, the Census collects information about the housing of people in Australia, and on other topics such as education, participation in the labour force, occupations and industries, marital status and family size. The range of topics included means that any particular topic can be examined in conjunction with other related topics. While some Census topics are covered by other sources, only the Census can currently provide information on a standard basis for the country as a whole, as well as for small geographic areas and small population groups.

The Census counts all people in Australia on Census night (excluding foreign diplomats and their families). This means that visitors to Australia are counted regardless of how long they have been in the country or how long they plan to stay, but that Australian residents who are overseas on Census night are not included.

People in Norfolk Island on Census night were counted for the first time in the 2016 Australian Census following passage of the Norfolk Island Legislation Amendment Act 2015. The Territories of Cocos (Keeling) Islands and Christmas Island have been included in the Australian Census since 1996. Expeditioners to Australian bases in the Australian Antarctic Territory (and other locations) are also included in Census counts.

The Census Post Enumeration Survey provides an independent measure of Census coverage through its estimate of undercount and overcount. Coverage and response rates are important measures in understanding Census data quality. The key indicators for the 2016 Census of Population and Housing support that the Census data is of high quality, with high response rates (95.1) and low levels of net undercoverage (1.0%).

The Census question on Aboriginal and Torres Strait Islander status is designed to determine the number, distribution and characteristics of people of Aboriginal and/or Torres Strait Islander origin. It is also used in estimation and projections of the Aboriginal and/or Torres Strait Islander population. The Census is the only comprehensive source of small area data on the Aboriginal and Torres Strait Islander population.

For all Censuses prior to 1971 respondents were asked to state their race and, where race was mixed, to specify the proportions of each. In the 1971 and 1976 Censuses, a question with response categories of European, Aboriginal, Torres Strait Islander and Other was included. Since 1981, a specific question has been asked to identify Aboriginal and Torres Strait Islander peoples.

The responses to this question are captured automatically from mark box responses on the form, so the risk of processing error is minimal. Where respondents identify with both Aboriginal and Torres Strait Islander origins, they were instructed to mark both the Aboriginal and Torres Strait Islander boxes. In cases where a respondent marked both No and Yes boxes, then the Indigenous Status was set to Not Stated. This treatment differs to that used in the 2011 Census where if both No and Yes mark boxes were selected, the responses were accepted in the order they appeared on the form and the extra response was rejected. This change in treatment aligns with the Indigenous Status Standard, 2014, Version 1.5 (cat. no. 1200.0.55.008).

For more information on definitional changes and Census questions, refer to the Census Dictionary, 2016 (cat.no. 2901.0).

For the 2011 Census and earlier Censuses, the ABS relied on a large field workforce to list every household across Australia. Field officers knocked on every door in an attempt to make contact with householders and to deliver paper Census forms or online Census login codes. The field officers not only delivered and collected Census material, but also recorded some characteristics about the houses in which the people lived.

For the 2016 Census, the ABS developed a new method that addressed the difficulties in recruiting field staff, as well as investing in the advantages and efficiencies of new technologies. Changes were designed taking into account international best practices in Census taking and building on the Australian public's increasing access to and use of the internet, and their willing support of the Census. The new method made three main changes from that used in earlier Censuses.

• The development of a national Address Register to support mailing out of materials to households across Australia. The Address Register was formed using the Geocoded National Address File (GNAF) as its base and then built on using information gained through visiting every address through a large canvassing exercise, in addition to analysing other available data. This register formed the basis of addresses to which information was mailed out.
• The postal delivery of an instruction letter detailing how to complete the Census online or how to request a paper form. Paper forms were then despatched and mailed back via Australia Post. This ensured that Census field officers only visited a minority of homes, where the use of the mail service was not considered viable, or where a Census form had not been returned.
• The use of a smarter online form. Many enhancements were made to the online form to improve quality and make it easier for respondents to complete. These enhancements are detailed in the Online form section.

As in previous Censuses, in 2016 there were a range of approaches used for collecting information from specific population groups. This included strategies to increase participation of remote Aboriginal and Torres Strait Islander peoples and urban Aboriginal and Torres Strait Islander peoples. These approaches were designed in consultation and collaboration with relevant communities and/or service providers to ensure the coverage of all people in Australia (including these specific populations) was as complete as possible.

Since 1976, measures have been adopted to maximise coverage of the Aboriginal and Torres Strait Islander population. These include specific Census awareness activities, greater use of Aboriginal and Torres Strait Islander staff, greater involvement of Aboriginal and Torres Strait Islander organisations, and better coordination of the related field operations. In remote areas, interview forms have been used to facilitate the enumeration of this population. 

The 2016 Discrete Communities and Remote Areas Strategy incorporated improvements to enumeration of Aboriginal and Torres Strait Islander people living in remote Aboriginal and Torres Strait Islander communities. At a broad level, the improvements for the 2016 Census included:

• earlier and ongoing engagement;
• a reduction in the overall enumeration period for Aboriginal and Torres Strait Islander communities;
• an increase in the number of field staff recruited; and
• a greater level of support to Aboriginal and Torres Strait Islander people requiring assistance in completing their form (in both urban and remote areas) 

For more information on the Discrete Community and Remote Areas Strategy in the Census Dictionary, 2016 (cat no. 2901.0).

For the 2016 Census the ABS also incorporated improvements to assist Aboriginal and Torres Strait Islanders living in urban communities to participate in the Census. As part of this strategy in pre-identified urban areas increased support and assistance was provided to Aboriginal and Torres Strait Islander people, including the option of collecting Census information through an interview.

There are four principal sources of error in Census data: respondent error, processing error, partial response and undercount. Quality assurance processes in the Census program aim to reduce error as much as possible, and to provide a measure of the remaining error to data users, to allow them to use the data in an informed way.

The publication Census of Population and Housing: Understanding the Census and Census data, Australia (cat. no. 2900.0) provides further information on the Cenus, Census data quality and Census topics.

The proportions of the population shown in the tables of this publication include 'not stated' responses in the denominator unless otherwise indicated. For example, the proportion of people in Australia who are of Aboriginal and/or Torres Strait Islander origin would be calculated by dividing the number of persons identified as Aboriginal and/or Torres Strait Islander in origin by the total population, and expressing the result as a percentage. The 'total population' includes records coded to 'not stated' unless otherwise indicated.

The Australian Bureau of Statistics (ABS) is committed to protecting the personal information it collects. Not only does the ABS have strong legislative protections that safeguard the privacy of an individual's information, we have a proud 100 year history of maintaining community trust in the way it collects, uses, discloses and stores your personal information collected in the Census.

The ABS has developed a technique to adjust counts to maintain confidentiality of information. This technique, known as perturbation, is applied to all counts, including totals, to prevent any identifiable data about individuals being released. These adjustments result in small introduced random errors and can mean that the rows and columns of a table do not sum to the displayed totals. However, the confidentiality technique is applied in a controlled manner that ensures the information value of the table as a whole is not significantly affected. Further information on the methodology of perturbation can be found in Confidentialising Tabular Output to Protect Against Differencing paper.

Perturbation can be a source of frustration to users because rows and columns do not add to totals, but this technique is implemented to protect personal information. Most tables reporting basic statistics will not show significant discrepancies due to perturbation. However, as the degree of complexity of a table increases, the need for perturbation remains and it will continue to be used in the release of 2016 Census data.

For 2006 and 2011 Census data, an additional 'additivity step' was applied that made further small adjustments to each table to ensure rows and columns added to totals. This extra adjustment meant that comparisons between tables which contained similar data items had minor discrepancies. In addition, as the tables at different geographic levels are adjusted independently, tables at the higher geographic level may not be equal to the sum of the tables for the component geographic units. Because of these inconsistencies, for 2016 Census data this additivity step has been removed.

It is important to acknowledge the difference between Census counts, which are provided in this publication and the Estimated Resident Population (ERP). ERP is the official measure of the population of Australia.

Estimates of the resident population are based on Census counts by place of usual residence, to which are added the estimated Census net undercount and the number of Australian residents estimated to have been temporarily overseas on Census night. Overseas visitors in Australia on Census night are excluded in this calculation. Post-Census ERP is obtained by adding to the estimated population at the beginning of each period the component of natural increase (on a usual residence basis) and the component of net overseas migration. For the states and territories, estimated interstate movements involving a change of usual residence are also taken into account.

After each Census, estimates for the preceding intercensal period are finalised (rebased) by incorporating an additional adjustment (intercensal difference) to ensure that the difference between the ERPs at the two 30 June dates in the respective Census years agrees with the total intercensal change.

ABS will publish 2016 Census-based preliminary estimates of the Aboriginal and Torres Strait Islander population in Australian Demographic Statistics, Mar 2017 (cat. no. 3101.0), released 27 September 2017. These preliminary estimates will be published by five year age groups, sex and state/territory of usual residence. Further disaggregation will be available when the final estimates of the Aboriginal and Torres Strait Islander population for 30 June 2016 are published in Population Estimates, Aboriginal and Torres Strait Islander Australians, 2016 (cat. no. 3238.0.55.001), scheduled for release in September, 2018.

For further information regarding Demography releases, see Australian Demographic Statistics publication, Dec 2016 (cat. no. 3101.0).