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New Geos: Australia - Geo Structure and Metro Areas
Wednesday, 12 Oct 2011 12:11 ET
By Isobel Rubin
June 2011 -- For Global Cities in Australia, we use statistical division-level data to estimate undefined metro-level data.

Official Geographical Structure

As defined by the Australian Bureau of Statistics' (ABS) Australian Standard Geographical Classification (ASGC) (July 2010 edition), there are seven alternative geographical structures for Australia.  The "main" structure is designed to meet user needs for social, demographic and economic statistics.  It is a six-level hierarchy of "spatial units" whereby each unit is covered by an assemblage of the next smaller type, with no gaps or overlaps.  That is, the nation's surface is covered by the nine states and territories, each state is covered by its respective statistical divisions, etc.

We base our data harvest on the Main Structure.  One of our nine metro areas is predicated on an ABS definition that uses the alternative UC/L structure, but translated to the Main Structure.

Table 1.  ASGC Main Structure and Moody's Analytics extension, abbreviations, counts of areas, wild card geography codes.

Name Abbv. Count Coverage Geo Code Wild Card
ASGC Main Structure, July 2010
Nation   1 1 IAUS
States and Territories S/T 9 9 IAUS_^^
Statistical Division SD 61 8 IAUS_^^^
Statistical Subdivision SSD 206 0  
Statistical Local Area SLA 1,389 0  
Census Collection District CD  Varies  0  
Moody's Analytics
Metropolitan Area MSA 0 9 IAUS_M^^^

In non-census years, CDs are undefined.  Because the Main Structure does not exactly match the political or administrative structures of the country, some of the counts are different than you might expect.

Historical Coverage in Data Buffet

Our Data Buffet coverage includes Australia the nation, the nine S/Ts, and eight of the 61 SDs -- namely, the Capital City Statistical Divisions.  (See tables 1 and 2.)  Coverage of metropolitan areas is separate.

Moody's Analytics Metropolitan Areas

In the United States, metropolitan statistical areas (MSAs) are officially defined, by the U.S. Office of Management and Budget, as specific aggregates of counties with economic identities.  Australia has no comparable standard.  Hence, for the purposes of our Global Cities product, we have defined our own.

Table 2. Moody's Analytics metropolitan areas mapped to AGSC's Statistical Divisions and Urban Centre/Localities.

Name MSA Geo Code SD Geo Code
Per ABS-defined Capital City SDs
Per ABS-defined UC/L-based metro areas

Eight or our metro areas are synonymous with one of AGSC's eight standardized Capital City SDs, which ABS defines as follows:

A Capital City SD (currently one in each capital city) should be defined, after consultation with planners, to contain the anticipated development of the city for a period of at least 20 years. This fixed SD boundary - as distinct from the moving urban centre boundary - delimits an area which is stable for general statistical purposes. It represents the city in a wider sense. This delimitation procedure cannot be applied to the separate urban centres within a Capital City SD.

Our ninth metropolitan area, the Gold Coast, is defined differently, using ABS's Urban Centre/Locality (UC/L) system.  This is a parallel alternative to the Main Structure.

In short: ABS defines the Gold Coast metropolitan area as conterminous with the Gold Coast-Tweed Heads (2006) UC/L, which comprises most of the Gold Coast SD (i.e., the SLAs in the former comprise most of the SLAs in the latter).  Therefore, we can reasonably define our own metro area (IAUS_MGOL) as conterminous with the SD (IAUS_GOL).  This is necessary because ABS reports historical data by SD, not by UC/L.

The system of Urban Centre/Localities is redefined at each population census (most recently, 2006). UC/Ls aggregate to cover only part of each state or territory, and hence, only part of Australia. The structure has three categories: Australia (the parts covered by UC/L only), Urban Centres/Localities (UC/L), and Census Collection Districts (CD). According to the ABS,

an Urban Centre is a population cluster of 1,000 or more people while a Locality is a population cluster of between 200 and 999 people. For statistical purposes, people living in Urban Centres are classified as urban while those in Localities are classified as rural. Each Urban Centre/Locality has a clearly defined boundary and comprises one or more whole CDs.