Survey Data Confidentiality


In accordance with the Census and Statistics Act 1905, all the data in TableBuilder are subject to a confidentiality process before release. This confidentiality process is done to avoid releasing information that may allow for identification of particular individuals, families, households, dwellings or businesses, without impairing the usefulness of the tables.

Care should be taken in analysing tables with cells that have a small count. No reliance should be placed on small number cells or cells with large percentage Relative Standard Error (RSE) values. Aside from the effects of the confidentiality process, sampling error and possible respondent and processing errors have greatest relative impact on small numbers and cells with large percentage RSEs.

When analysing a table of means or sums of a continuous variable, it is recommended that the table be compared to the corresponding table of counts of units with a valid response for that continuous variable. No reliance on estimates of means or sums should be placed on cells with a large RSE or for which the corresponding cell count is small.

A technique has been developed to randomly adjust cell values. Random adjustment of the data is considered to be the most satisfactory technique for avoiding the release of identifiable data in a TableBuilder product. When the technique is applied, all cells are adjusted to prevent any identifiable data being exposed. These adjustments result in introduced random errors. However the information value of the table as a whole is not impaired.

For some but not all datasets on TableBuilder, an additional technique has been implemented that ensures tables produced from the dataset remain additive. Users should consult the dataset specific manual to ascertain whether this ‘additivity’ technique has been implemented for that dataset.

For datasets where the ‘additivity’ technique is implemented, secondary adjustments are made to cell values so that each table of estimates of counts will be internally consistent. (‘Internally consistent’ means that the interior cells add up to the totals). The tables at different geographic levels are adjusted independently, and tables at the higher geographic level may not be equal to the sum of the tables for the component geographic units. A table of estimates of sums will in general not be internally consistent. Also, the technique may introduce discrepancies between tables with similar data items.

RSE estimates do not take into account the effects of the additivity technique. To ensure consistency with the cell values, the additivity technique may scale some RSE estimates.

For datasets where the ‘additivity’ technique is not implemented, a table of estimates of counts or proportions will in general not be internally consistent.