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18.3 Estimates from the 1996 Census were released in two phases, and a similar approach is proposed for the 2001 Census. For the 1996 Census, most data (approximately 80%) were released approximately 11 months after the census was conducted, with the remaining data released within the following twelve months. A number of products are used to release data from the census. These include:
The 'Selected Characteristics' series, and the 'Social Atlases' are examples of census publications. The Selected Characteristics series provides census counts for small areas (SLAs1), and has been produced in a similar format since 1911. The series includes, for each SLA, data on selected social and housing characteristics, educational and labour force characteristics, and urban centre and localities characteristics. The Social Atlases give a geographic perspective on the characteristics of the population.
1. SLAs (Statistical Local Areas) are spatial units used to disseminate statistics from the census. They comprise one or more census collection districts (see below) and, in aggregate, they cover the whole of Australia without gaps or overlaps. For further information, see paragraph 15.41.
18.4 The census collects data on a range of topics. The criteria used to select topics for inclusion on the census form are outlined below (paragraph 18.7). The 2001 Census will collect information on the following topics:
SCOPE AND COVERAGE
18.5 The census aims to enumerate all persons residing in Australia on census night. The census is undertaken on a 'de facto' residence rather than 'de jure' residence basis: i.e. it is based on location on census night rather than on a usual residence basis.
18.6 Persons residing in the external territories of Cocos (Keeling) Islands and Christmas Island were included in the census for the first time in 1996. Persons enumerated in the census include almost all persons in Australia on census night, whether temporary or permanent residents. The only exceptions are diplomatic personnel of other nations resident in Australia. By definition it also excludes Australian residents temporarily overseas.
18.7 Topics for inclusion in the census must meet the following criteria:
18.8 Prior to a census there is considerable consultation with clients. Client consultation for the 2001 Census was initiated by the release of Information Paper 2001 Census: ABS Views on Content and Procedures (Cat. no. 2007.0). This paper described the proposed topics to be included and for which the ABS was seeking further views. It was widely distributed and its availability widely advertised.
18.9 On receipt of submissions, a series of consultative meetings are held, culminating in seeking advice from the Australian Statistics Advisory Council. A report of the final recommendations is then prepared for approval by Cabinet.
18.10 Since the first national census in 1911, the content of censuses has changed. Some topics have been included in each census since 1911, for example age, marital status and religion, while others have been included or excluded depending on the importance of the topic at the time. For information on topics included in each census held from 1911 to 2001, see How Australia Takes a Census (Cat. no. 2903.0).
18.11 The census is self-enumerated. Forms and information booklets are distributed by census collectors to every household in Australia prior to census night. The completed forms are then collected in the week or so following census night. The conduct of the census is complex. Various aspects of the collection methodology are discussed below. For more detail see How Australia Takes a Census (Cat. no. 2903.0).
18.12 The date the census is conducted is carefully chosen. Recent censuses have been conducted in August, the month in which the least population displacement occurs. The day of the census varies, and is chosen to avoid school and other major holidays.
18.13 A hierarchical structure of temporary staff is used to deliver and collect census forms. All staff are appointed under the Census and Statistics Act 1905 and are subject to the strict confidentiality provisions of the Act.
18.14 ABS State and Territory Offices are responsible for the management of all field staff in their State or Territory. The majority of the workforce, just under 28,000 people, are the census collectors. These deliver a Census Form and Census Guide to every household in their collection district2 prior to census night. They are also responsible for collecting forms following Census night.
2. The collection district (CD) is the basic geographic unit of collection. A CD is generally a census workload area that one Collector can cover, delivering and collecting census forms in a specified period. For further information see paragraph 15.41.
18.15 As the census is self-enumerated, there is a heavy reliance on the ability of respondents to correctly interpret questions and to answer in the desired manner with the appropriate amount of detail. Collectors are encouraged to make contact with householders, since a high level of householder contact contributes to high response and a low under-enumeration rate. On receipt of the census forms from householders, census collectors are instructed to briefly scan them to ensure that they have been completed.
18.16 In total, more than 32,000 temporary field and collection staff will be involved in the delivery and collection of forms from the 2001 census. These staff need to be recruited, trained, supplied with material, supervised and paid on completion of their work. The development and logistics behind the census are enormous and require careful planning and implementation.
FORM DESIGN AND TESTING
18.17 A program of tests is conducted before each census to decide on the layout and question wording for the census form. A series of seven tests, including a dress rehearsal, was undertaken for the 2001 Census to make the forms as easy as possible for respondents to complete.
18.18 In addition, considerable consultation takes place among a variety of work groups within the ABS to ensure that:
18.19 Significant investment is made in public communication and media relations activities. Specialist staff are employed for the census collection period, and an advertising campaign prior to the census indicates the importance of the census and how the community is expected to cooperate to ensure its success.
18.20 Public figures are recruited to lend their support to the Census. In 1996, Census day was the day after the closing of the Atlanta Olympic Games. The opportunity was taken to have the anchorman of the Olympic telecast make a brief statement supporting the census each evening.
PROCESSING OF CENSUS FORMS
18.21 A special Census Data Processing Centre is set up each census with the specific task of processing the completed census forms as quickly as possible and thereby achieving the timely release of results.
18.22 Completed census forms are examined for completeness and consistency. Write-in responses on family, qualification and occupation are coded to the appropriate classification categories.
18.23 In the case of partial non-response, imputation is undertaken for sex, age, geographic area of usual residence and marital status in accordance with predefined algorithms. The remaining data items are set to 'not stated' unless other information exists which allows the determination of Aboriginal/Torres Strait Islander origin and Labour Force Status.
18.24 As with other statistical collections, the ABS is concerned to see that high quality data are obtained from the census. To this end, extensive effort is put into the form design, collection procedures, public awareness campaign and accurate processing of the information collected.
18.25 The method employed to obtain information in the census involves 'self-enumeration' in which each household is asked to complete the census form with relatively little assistance from the census collector. To make sure that this approach is successful, a series of tests3 is conducted before each census to gauge public reaction to the form and the questions it contains.
3. For further information see paragraph 18.17 above.
18.26 As well as making sure that the right questions are asked, it is essential for the achievement of quality census data that everyone understands the importance of being counted and of giving the right answers in the census. A crucial factor in this respect is the public awareness campaign, discussed above in paragraph 18.19.
18.27 Once the forms are in the Census Data Processing Centre, quality assurance procedures are implemented at all phases of processing to maximise the accurate recording of information collected and to eliminate as far as possible any inconsistencies in coding responses. Coding procedures, indexes, processing systems and training of staff are the key areas where changes can lead to improved data quality during processing.
18.28 The census, like all statistical collections, is subject to a number of sources of non-sampling error4. However, testing has indicated that the effect of these errors is generally slight, although it could be more significant for analyses of data for small groups, or for very detailed cross classifications.
4. The Census of Population and Housing, like other types of fully enumerated collections, is not subject to sampling error - see Chapter 16 for further information.
18.29 The four most significant sources of non-sampling error for the census are: undercounting; partial response; respondent error; and processing error. These are discussed further below.
18.30 Despite efforts to obtain full coverage of people and dwellings, 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 referred to as undercounting.
18.31 As well as affecting the total population counts, undercounting can bias other census statistics because the characteristics of missed people are different from those of counted people. In Australia, rates of undercounting vary significantly for different population groups depending on factors such as age, sex and geographic area. A measure of the extent of undercoverage is obtained from a sample survey of households undertaken shortly after the census, called the Post Enumeration Survey. Undercounting of people in the 1996 Census was estimated to be 1.6% for Australia as a whole.
18.32 People who are counted in the census do not necessarily answer all the questions which apply to them. While questions of a sensitive nature are generally excluded from the census, all topics have an element of non-response. However, this element can be measured and is generally low. In those instances where a response is not provided, a 'not stated' code is allocated, with the exception of non-response to age, sex, marital status and the statistical local area of usual residence. As these data are used in population estimates, these variables are imputed, using other information reported on the census form and specially constructed random tables based on the distribution of the population according to these variables at the previous census.
18.33 Most occurrences of respondent error are detected and corrected during editing. However, such procedures cannot detect and correct all errors, and some remain in the final output.
18.34 Errors created during the processing of the census are kept at an acceptable level by means of quality assurance procedures. These involve sample checking during coding operations, and taking corrective action where necessary.
Evaluating the outcome
18.35 After the census, an evaluation of the data is carried out to inform users about their quality, and to help plan the next census. Evaluation includes investigation into the effects of partial response, consistency checks between related questions, and comparisons with data from other sources. Much of the information gathered about the quality of census data is distributed in the form of commentary contained in census products or in published working papers reporting on the evaluation of census data quality.
Introduced random adjustments
18.36 Minor adjustments are made to the information to allow the maximum detailed census data possible to be released without breaching the confidentiality of data reported by individual respondents. For this reason, great care should be taken when interpreting data in small cells, since possible respondent and processing errors have a greater proportional impact on them than on larger cells.
RELIABILITY OF THE ESTIMATES
18.37 Estimates from the census are subject to non-sampling error. For further information see paragraph 18.29 above.
DATA COMPARABILITY OVER TIME
18.38 In order to provide a high degree of consistency and comparability over time, changes are made as infrequently as possible to collection methods, collection concepts, data item definitions, frequency of collection, and analysis methods.
18.39 Table 18.1 shows the major changes to the labour-related data items in the census over its history.
18.1 MAJOR CHANGES TO LABOUR-RELATED DATA ITEMS IN THE CENSUS OF POPULATION AND HOUSING
18.40 For further details, contact the Assistant Director, Population Census Development and Evaluation, on Canberra (02) 6252 5942.