ANALYSING THE ACLD - UNDERSTANDING CONSISTENCY BETWEEN WAVES
The ACLD is a longitudinal dataset using data from successive Censuses.
While the Censuses had predominantly the same questions and were processed in a similar way, there were some differences between them.
Users are encouraged to read Understanding the data pages in Census of Population and Housing: Understanding the Census and Census Data, Australia, 2016 (cat. no. 2900.0), information in How Australia Takes a Census, 2011 (cat. no. 2903.0), and the 2006 Census data quality page for information to assist with using and interpreting specific data items across time.
For example, a number of changes were made to how industry of employment information was collected for the 2016 Census. The ABS advises this data is not directly comparable to the previous Census Industry of employment data, and should not be used to measure longitudinal transitions between industries from 2011 to 2016. For further information refer to Industry of Employment (INDP) in Census of Population and Housing: Understanding the Census and Census Data, Australia, 2016 (cat. no. 2900.0).
Other 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.
A small percentage of linked records have inconsistent data, such as a different country of birth at the two time points or an age inconsistency of more than one year. Inconsistencies may be due to:
- false link - the record pair does not belong to the same individual
- reporting error - information for the same individual was reported differently in 2006, 2011 and in 2016
- processing error - the value of a data item was inaccurately assigned or imputed during processing.
In most analysis, the effect of inconsistent information has a very small impact. Characteristics from either the 2006, 2011 or 2016 data can be used in tables and some exploration of consistency over time will assist in drawing appropriate conclusions.
For further information about the ACLD linkage methodology refer to Information Paper: Australian Census Longitudinal Dataset, Methodology and Quality Assessment, 2006-2016 (cat. no. 2080.5).
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 Items list.