Australian Bureau of Statistics
2901.0 - Census Dictionary, 2011
Latest ISSUE Released at 11:30 AM (CANBERRA TIME) 23/05/2011
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Derivations and imputations
Derivation is the process where some variables are assigned values based on responses to other questions, or (where no response has been provided) from other family members present in the same dwelling.
Variables that may be derived from responses given by other family members present in the same dwelling are:
In addition, the derivation process is used to create new variables by combining responses from a number of questions. Variables which are created this way include:
Where no Census form is returned, the number of males and females in 'non-contact' private dwellings will be imputed. In addition, the following key demographic variables may also be imputed, if they are 'Not stated':
The methodology for imputation is tailored to two situations. Firstly, where no Census form has been returned and secondly where a partially completed form was returned.
No Census form returned - private dwelling: Where a Census collector has identified that a private dwelling was occupied on Census Night but a Census form was not returned, the number of males and females normally in the dwelling and their key demographic variables may require imputation. In these cases, the non-demographic variables are set to 'Not stated' or 'Not applicable'.
The 'No Census form returned' scenario has two variations. Firstly, where no form was returned but the collector was able to ascertain the number of males and females from a resident of the dwelling, or in a small number of cases a building manager or neighbour. And secondly, where no form was returned and the number of males and females remains unknown.
For records where the number of males and females is unknown, two imputation processes are required. Initially these records must have their number of males and females imputed using hotdecking. Then a second imputation (also using hotdecking) is run to impute the key demographic variables.
To hotdeck the number of males and females, the donor records must meet several conditions:
In the next process, the records which have just had their number of males and females imputed, are subjected to the same hotdecking process as those records where the number of males and females had been ascertained.
This hotdecking process imputes the key demographic variables. Again the donor records must meet several conditions:
The key demographic variables are then copied from the donor records to the records requiring imputation.
No Census form returned - non private dwelling: Where a person in a non-private dwelling did not return a form, their demographic characteristics are copied from another person in a similar non-private dwelling using Type of Non-Private Dwelling (NPDD).
Census form returned: Where a form was returned, some or all of the demographic characteristics may require imputation. If Registered Marital Status and/or Place of Usual Residence are 'Not stated' they are imputed using hotdecking, whereas Age is imputed based on distributions obtained from previous Censuses.
Registered Marital Status imputation is carried out by finding a similar person in a similar responding dwelling based on the variables:
Registered Marital Status is only imputed for persons aged 15 years and over, and set to 'Not applicable' for persons aged under 15 years.
Where a complete usual address on Census Night is not provided, the information that is provided is used to impute an appropriate Mesh Block (as well as Statistical Area Level 1 and Statistical Area Level 2). A similar person in a similar dwelling is located, and missing usual residence fields are copied to the imputed variable.
These are based on the variables:
For 2011, dwelling address derivation and imputation is being introduced. Private dwellings that have an incomplete or no address will have a mesh block code derived from adjacent dwellings listed in the collector record book. If a dwelling mesh block code is unable to be derived the dwelling will be imputed into a Mesh Block located within the relevant collector workload. Imputation of the Mesh Block code is a probability proportionate method based on distributions of coded dwellings across mesh blocks contained within a collector workload. These distributions are based on Dwelling Structure (STRD).
For previous censuses the output geographic boundary (Collection District (CD)) was the same as the collection geographic boundary and therefore a dwelling address was automatically coded to the code of the collector's district.
Records that have required imputation can be identified using the Imputation flags:
See also Imputation variables.
This page last updated 1 September 2011
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