MAIN STRUCTURE OF THE AUSTRALIAN STANDARD GEOGRAPHICAL CLASSIFICATION (ASGC) PURPOSE The Main Structure of the ASGC is used to collect and disseminate a broad range of ABS social, demographic and economic statistics Although the Main Structure is the most widely used and has broad application, the other structures are equally important to their own purposes THE STRUCTURE The Main Structure has five hierarchical levels at Population Census times, comprising in ascending order: CDs-SLAs-SSDs-SDs-S/Ts In non-census years, CDs are undefined and the Main Structure thus has only four levels of hierarchy In this structure, CDs aggregate to form SLAs, SLAs aggregate to form SSDs and this aggregation principle continues up the remaining hierarchical levels At each hierarchical level, the component spatial units (e.g SLAs) collectively cover all of Australia without gaps or overlaps Tables Details of the Main Structure are shown in the following tables Broad Main Structure (showing three hierarchical levels: S/T-SD-SSD) Example: S/T SD SSD NEW SOUTH WALES Hunter Newcastle Hunter SD Bal 10 05 10 Detailed Main Structure (showing four hierarchical levels: S/T-SD-SSD-SLA) Example: S/T SD SSD 10 05 SLA NEW SOUTH WALES Hunter Newcastle 1720 4650 Cessnock (C) Lake Macquarie (C) 2700 3050 Hunter SD Bal Dungog (A) Gloucester (A) 10