9309.0 - Motor Vehicle Census, Australia, 31 Mar 2009 
Quality Declaration
Quality Declaration ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 17/11/2009
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EXPLANATORY NOTES
4 Vehicles on register are defined as those vehicles registered at the date of the census, or had registration expire less than one month before that date. 5 Motor vehicle registration statistics are derived from data made available by various state and territory motor vehicle registration authorities and reflect the information as recorded in registration documents. 6 Vintage and veteran vehicles are excluded from vehicle counts in the published data, but are available for consultancy data requests. These vehicles are identified using a unique insurance code, with the following exceptions:
7 The estimated proportion of motor vehicles, excluding motor cycles, taken off the register since the previous MVC is referred to as the attrition rate. The attrition rates in the following table have been calculated using new motor vehicle sales data.
METHODOLOGY 8 The 2009 Motor Vehicle Census is a count of all vehicles registered with a state or territory motor vehicle registration authority (MVR) at 31 March 2009. The snapshot date has consistently been 31 March since 2001. The Australian Bureau of Statistics (ABS) receives the data from the MVRs. At this stage all records are compared to the previous MVC data for vehicles that match (on-going registrations) and relevant details are updated. The matching is based primarily on a unique identifier given by the registries to each record. After the primary match is done, a secondary match is run based on the Vehicle Identification Number (VIN), engine number, chassis number, year of manufacture and bodycode to improve the number of matched records. 9 The un-matched records (new vehicle registrations) undergo editing of such items as bodycode, make, model, year of manufacture, weight, heavy vehicle code, postcode and fuel. 10 The editing of on-going registrations is limited as these records have been edited in past years. Finally, aggregate data is checked across time, states and vehicle types to ensure coherency. DATA QUALITY 11 The size of the registered motor vehicle fleet (over 15 million vehicles) dictates that quality assurance of each record is not possible. Considerable effort is made, both by motor vehicle registration authorities and the ABS, to improve data quality. This has been done through the introduction of improved processing and classification systems and the incorporation of additional internal checking to ensure the vehicle counts track consistently in a time series when compared to previous MVCs. While these have improved data accuracy, there remains some variation in the reporting from different state and territory registries and hence care should still be taken when comparing data across jurisdictions. The ABS recognises the importance of motor vehicle statistics to a large variety of statistical users. While the data are made available at a detailed level, the quality of this detailed data is less certain, therefore the ABS is unable to guarantee that it is necessarily sufficient for all purposes for which it is used. 12 For vehicles manufactured during or after 1990, the statistics in this publication are based on procedures using the VIN, adopted by state and territory motor vehicle registration authorities. The VIN system allows accurate identification of the make and model of a vehicle, which can then be used to better identify the vehicle type. Vehicles manufactured earlier than 1990 generally do not have a VIN. For these earlier vehicles, standard ABS makes and models were produced from registry make and model data using information such as engine number and chassis number. 13 Each year, for new vehicle registrations, vehicle model description for each Registry is converted to a standard ABS model. This is necessary as model descriptions can vary between Registries. Resource constraints affect the amount of model conversion that can be carried out, resulting in some vehicles being left with a blank model which is then coded to 'model unknown'. Data confrontation 14 While there are no data sources available in which to directly assess the quality of MVC data, new motor vehicle sales data and population data provide an indication of data quality as they give some context to the size of the motor vehicle fleet. Assessing the quality of data by comparison against other datasets is known as data confrontation. The ABS has been using sales of new motor vehicles data and estimated resident population (ERP) data to 'confront' MVC data for several years. New Motor Vehicle Sales (NMVS) 15 Sales of new motor vehicles can be compared with data from the MVC based upon the year of manufacture. The following assumptions have been made:
16 Therefore, it can be assumed that vehicles manufactured in 2008 (as reflected in 2009 MVC data) would most likely have been sold in the period between 1 April 2008 and 31 March 2009 (as captured by sales of new motor vehicles data). Similarly, vehicles manufactured in 2007 would have been sold between 1 April 2007 and 31 March 2008, and so on. 17 The graph below shows the relationship between sales of new motor vehicles and MVC registrations of vehicles manufactured in the year preceding the snapshot date. Estimated Resident Population (ERP) 18 The table below shows a comparison of growth on a state/territory basis for both the MVC and ERP. Over the past few years, strong motor vehicle sales have meant that the growth in motor vehicle registrations has been higher than the growth in ERP. However, growth in MVC and ERP has tended to be in the same direction. STATISTICAL GEOGRAPHY 19 The only geographic data available from the MVC are postcode of owner and state or territory of registration. 20 If analysing regional data based on postcodes, the following considerations need to be taken into account:
RELATED PUBLICATIONS AND PRODUCTS 21 Users may also wish to refer to the following publications and products which contain information relating to motor vehicles in Australia:
ABS DATA AVAILABLE ON REQUEST 22 As well as the statistics included in this publication, the ABS has other relevant data available on request. Inquiries should be made to the National Information and Referral Service on 1300 135 070. Document Selection These documents will be presented in a new window.
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