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Self-enumeration imposes limits on the types of topics and questions that can be included in the Census. Topics which require complex questions or question sequencing are not suitable for a Census, as the responses obtained may not be reliable. There is also the need to limit the total number of questions asked in order to minimise the amount of time it takes for a respondent to complete the Census form.
Some topics are included in the Census to meet legislative requirements to provide a reliable base for estimation of the population of each of the states, territories and local government areas for electoral purposes and the distribution of government funds. They are: Sex, Age, Registered Marital Status, Indigenous status, Usual residence at Census time, and Internal Migration.
Other topics are selected for inclusion in the Census following extensive community consultation. Topics are selected based on the following criteria:
Question and form design
The Census form is designed so that questions are easily understood and simple for respondents to answer. Most questions are answered by selecting an option, although some questions require free text responses.
Questions are tested via focus groups and cognitive interviews to ensure they are clear, well worded and can be answered on behalf of others. Following the successful completion of this cognitive testing, field tests are conducted in various cities and rural locations. These assist in assessing how the questions and the Census form work in a real environment.
Specific tests are also conducted on the usability and functionality of the online form.
Raising public awareness
To achieve high quality Census data it is essential that people understand the importance of being counted and of giving the right answers in the Census. Raising public awareness through advertising and community briefings contributes to high levels of participation in the Census. It helps people understand the benefits to the community of complete and accurate Census counts and minimises intentional respondent error.
The public relations campaign also aims to make people aware of the help that is available for people who have problems filling out their Census form. Help is available within the online form, on the Census web site, and from the Census Inquiry Service telephone help line. This assistance helps to reduce respondent error and contribute to high quality data.
Much of Census data is recorded using automatic processes, such as scanning, Intelligent Character Recognition and other automatic processes. Quality assurance procedures are used during Census processing to ensure processing errors are kept at an acceptable level. Sample checking is undertaken during coding operations, and corrections are made where necessary.
Once paper forms are received, they are checked for damage and errors, such as tears, multi-mark responses and illegible handwriting. Where required, these problems are fixed manually to assist the automatic coding processes.
Most responses are coded automatically using official classifications with legal value checks built into the system. In addition, a random sample of codes is checked manually against the original response on the form. Errors are more likely to arise during automatic coding of 'write in' answers. Clerical staff resolve problems that arise if text responses cannot be automatically matched to the index of possible responses. Their work is subject to a quality management process to ensure that errors are not being made.
The completed data are put through a series of automated checks to ensure internal consistency. The data are also scrutinised for changes over time, by comparison with previous Census data and other data sources, and across categories, where expected trends can be identified, and unexpected trends investigated.
In preparing Census data for output, various derivations and recodes are applied to the data to produce the variables listed in this dictionary. Data are processed further to create the range of Census data products. A series of checks occur at each stage of the output process to ensure data consistency and accuracy.
When completing their Census form, some people do not answer all the questions which apply to them. While questions of a sensitive nature are generally excluded from the Census, all topics have a level of non-response. However, this level can be measured and is generally low. In those instances where a householder fails to answer a question, a 'not stated' code is allocated during processing, with the exception of non-response to age, sex, marital status and place of usual residence. These variables are needed for population estimates, so they are imputed using other information on the Census form, as well as information from the previous Census.
The goal of the Census is to obtain a complete measure of the number and characteristics of people in Australia on Census night and their dwellings, but it is inevitable that a small number of people will be missed and some will be counted more than once. In Australia more people are missed from the Census than are counted more than once. The net effect when both factors are taken into account is an undercount.
During the delivery and collection of Census forms to households, quality assurance field procedures are put into practice to ensure the maximum number of households are included in the Census.
Every effort is made to ensure that all households receive a Census form and that these are completed and returned. The "Digital First" approach involves mailing information to households in most areas of Australia. Those households who do not respond will receive reminder letters and/or visits by Field Officers. For example, Field Officers are required to return to a household up to a total of five times after Census night in urban areas and up to three times in rural areas to attempt to obtain a response. This also applies where a householder states they returned their form via electronic lodgement (online) or mail but the Field Staff have not received notification of the receipt of the form.
All forms are registered to the dwelling they were delivered to, so that data processing staff can account for all forms received as well as those still to be returned by mail or by electronic lodgement (online). Ensuring all dwellings are contacted and all persons have provided a response is a critical measure of the completeness of the Census.
Some groups of people in the population are at risk of being undercounted in the Census. These include Aboriginal and Torres Strait Islander people, ethnic groups who have trouble reading or speaking English, people experiencing homelessness, travellers and other more transient population groups such as young people and fly-in fly-out workers. In addition, some areas are more difficult to enumerate, including areas with secure apartment buildings, discrete communities and remote areas. Targeted enumeration strategies have been developed to ensure a more complete count of these groups, dwellings and areas. Strategies are also in place to ensure accessibility to Census forms via the most appropriate means for people with disabilities.
A measure of the undercount in the Census is obtained from a sample survey of households undertaken shortly after the Census, called the Post Enumeration Survey. It collects information about where people were on Census night and their characteristics, which are compared to the actual Census forms. The Post Enumeration Survey for the 2016 Census indicated a net undercount of 226,407 persons or 1.0% of the population, i.e. the PES population estimate was 226,407 more persons than was counted in the 2016 Census. This was an improvement over a net undercount of 1.7% for the 2011 Census. Post Enumeration Survey results are discussed in more detail in Census of Population and Housing: Details of Overcount and Undercount, Australia, 2016 (cat. no. 2940.0).
Information from the Post Enumeration Survey are used to evaluate the effectiveness of Census collection procedures and data processing, so improvements can be made for future Censuses.
Quality Assurance of Census Products
Decisions about how and what is released from each Census are influenced by feedback from users of Census data. The ABS conducted a review in 2014 to gain feedback about the 2011 Census products. The review confirmed that users are generally satisfied with the current products and elicited a number of suggestions to improve them, including upgrades to improve stability and performance.
Introduced random adjustment
Individual Census records are confidential. Before Census data are released, small random adjustments are made to allow the maximum amount of detailed Census data possible to be released without breaching confidentiality. Consequently, care should be taken when interpreting cells with small numbers, since randomisation, as well as possible respondent and processing errors, have a greater impact on small cells than on larger cells (see also 'Introduced random error' in the Glossary section).
Where to Find Data Quality Information
For the 2016 Census, data quality information will be available with the Census data as they are released. Census of Population and Housing: Understanding the Census and Census Data, Australia, 2016 (cat. no. 2900.0) will include information on non-response rates and data quality statements.
Further analytical and evaluation papers will also be made available to address other data quality issues that require investigation. They will be released at www.abs.gov.au/census.