QUALITY DECLARATION

INSTITUTIONAL ENVIRONMENT
RELEVANCE
TIMELINESS
ACCURACY
COHERENCE
INTERPRETABILITY
ACCESSIBILITY


INSTITUTIONAL ENVIRONMENT

The Australian Census Longitudinal Dataset (ACLD) is released in TableBuilder and as a microdata product in the ABSDL. Microdata files are released in accordance with the conditions specified in the Statistics Determination section of the Census and Statistics Act 1905. This ensures that confidentiality is maintained whilst enabling micro level data to be released. More information on the confidentiality practices associated with TableBuilder can be found on the Confidentiality page. To protect confidentiality of data within the ABSDL, users are supervised at all times and must not bring mobile phones, cameras, USB keys, laptops, palm pilots or similar transmission or storage devices into the secure location. All outputs produced by users in ABSDL are manually cleared for release after the session.

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

RELEVANCE

Data for the Census of Population and Housing used in this product were collected on 8 August 2006 and 9 August 2011. The scope of the Census is all persons enumerated in Australia on Census night excluding certain diplomatic personnel of overseas governments. In addition persons who were overseas visitors on Census Night were excluded from the scope of the 2006 ACLD sample.

The Census collects information on demographics, income, labour force, unpaid work, dwelling characteristics and family and household relationships.

For more information, see How Australia Takes a Census, 2011 (cat. no. 2903.0).

TIMELINESS

The Census of Population and Housing is conducted every five years. For further information see the publication How Australia Takes a Census, 2011.

The first wave of Census data for the ACLD was from 2006 and the second from 2011. It is envisaged that the 2016 Census and subsequent Censuses will be added in the future, as well as administrative data sets.

ACCURACY

The ACLD was created using data linkage techniques without name and address but with other characteristics from the Census. It was based on a 5% random sample from the 2006 Census (979,661 records) of which 82% (800,759) were linked to a 2011 Census record. The false link rate is estimated at around 5-10%.

Sampling error occurs because only a small proportion of the total population is used to produce estimates that represent the whole population. Sampling error refers to the fact that for a given sample size, each sample will produce different results, which will usually not be equal to the population value. There are two common ways of reducing sampling error - increasing sample size and utilising an appropriate selection method (for example, multi-stage sampling would be appropriate for household surveys). Given the large sample size for the ACLD (1 in 20 persons), and simple random selection, sampling error is minimal.

The ACLD sample was weighted to the Estimated Resident Population in scope of both the 2006 and 2011 Censuses. The weights adjust for missed links and Census undercount.

Information on methodology, linkage quality and weighting can be found in Information Paper: Australian Census Longitudinal Dataset - Methodology and Quality Assessment, 2006 and 2011 (Cat. No. 2080.5). Information on the weighting of the ACLD has since changed with the update of the ACLD file that was released on 11 February, 2016. For information on the current weighting please see the Sample Methodology section of this publication.

Steps are taken to confidentialise the data made available on TableBuilder in such a way as to maximise the usefulness of the content while maintaining the confidentiality of respondents selected in the ACLD sample. As a result it may not be possible to exactly reconcile all the statistics produced from the microdata with other published statistics. Further information about the steps taken to confidentialise the microdata can be found in TableBuilder confidentiality.

Estimates of migrants in the ACLD using the Settlements Database (SDB) information may differ from the estimates produced in the ACMID for several reasons:

• the ACLD is a 5% random sample from the 2006 Census population, not the 2011 Census population;
• more recent migrants, that is, those that arrived between the 2006 and 2011 Censuses, are not included in the sample;
• linked records in the ACLD were benchmarked to the population that was in scope of both the 2006 and 2011 Censuses;
• the SDB information was merged to the 2011 Census records of people that were able to be linked (and not all records were able to be linked).

Due to these reasons above and other quality issues in the ACLD, estimates of migrants using the SDB information should generally be treated with caution.

COHERENCE

The ACLD microdata contains a large number of data items and in some cases the level of detail has been collapsed from that described in the Census Dictionary. For more information on the level of detail provided, please see the associated data item list.

While the 2006 and 2011 Censuses had predominantly the same questions and were processed in a similar way, there were some differences between them.

Notable data items that are different between Census years are personal, family and household income. Income was collected in ranges and these ranges are different in different Census years. The ACLD does not include an adjustment to income data for inflation.

Some data items were derived differently between Censuses. To aid comparability, the 2006 variable was re-derived to make it consistent with the 2011 derivation.

2006 Geography was originally disseminated according to the Australian Statistical Geography Classification. There were radical changes in the geography standard between 2006 and 2011 leading to the formation of the Australian Statistical Geographic Standard. In order to facilitate comparison, a 'best fit' of 2006 collection districts to align with the 2011 geographic boundaries was created, however in some cases this will be an approximation only.

The exception is Remoteness Areas where no adjustment was made and 2006 boundaries and definitions were applied for usual address for that time period.

For more information on the differences between the 2006 and 2011 Census see What's new for 2011?

INTERPRETABILITY

This publication should be referred to when using the microdata. It contains information on the Sample Methodology, File Structure, Using the ACLD in TableBuilder, The ACLD in the ABS Data Laboratory, Conditions of use and the Data items list.

Detailed information on methodology, linkage quality and weighting can be found in Information Paper: Australian Census Longitudinal Dataset - Methodology and Quality Assessment, 2006 and 2011 (Cat. No. 2080.5). Information on the weighting of the ACLD has since changed with the update of the ACLD file that was released on 11 February, 2016. For information on the current weighting please see the Sample Methodology section of this publication.

The ABS publishes extensive information on Census Data Quality.
ACCESSIBILITY

The Australian Census Longitudinal Dataset, 2006-2011 can be accessed throughTableBuilder and the ABS Data Laboratory.

This microdata product is available to approved users. Users wishing to access the microdata should read the How to apply for Microdata web page, before applying for access through the Registration Centre. Users should also familiarise themselves with information available via the Microdata web pages.

Any questions regarding access to microdata can be forwarded to microdata.access@abs.gov.au or phone (02) 6252 7714.