Australian Census of Population and Housing Dissemination Strategies UNSC Seminar February 2011 Gillian Nicoll Australian Bureau of Statistics

ABS Census Web Product Range

Client Segments Tourists –QuickStats, MapStats Harvesters –Census Tables, Profiles, CDATA Online Miners –TableBuilder

TableBuilder High end application for experienced users Online tool which allows the creation of customised tables Create custom tables direct from output record file which contains data for all census topics Provides users with highest degree of freedom in selecting and combining data items and geographical areas for cross-tabulation Create tables, maps and charts Dynamically confidentialises data

What can happen when releasing fine level data Repeated requests for the same table – random perturbation could produce different versions of the same table – comparing cell values may reveal information about the original unconfidentialised table Differencing – the difference between tables for similar sub- populations may reveal data for a much smaller population group

Automatically Protecting Tables in TableBuilder Aims of the method used – protects against the risks (previous slide) – allows users flexibility to specify tables for any data items at any of the standard geographic structures – allows users to create their own geographical areas from combinations of the standard geographical units – allows tables to be created at three different levels (people, families, and dwellings) – should not change the data too much so that the tables are not useful for analytical purposes – completes the confidentialisation on the fly and in a reasonable amount of time

Automatically Protecting Tables in TableBuilder The method comprises two modules – perturbation module that uses a cell level key that is used to determine the perturbation that is applied to the cell this method ensures that each cell receives the same perturbation whenever it appears in any table even if it appears in different tables – module that restores additivity to the perturbed tables so that each table makes sense to users Further technical information available