Where do Motor Vehicle Sales Statistics Come From?
Motor vehicle sales figures are produced by the Federal Chamber of Automotive Industries (FCAI), which collects data from all of its members on the sales of new vehicles, excluding motorcycles, plant and equipment and unpowered vehicles. For more information refer to the information paper Developments in New Motor Vehicle Statistics linked above.
Seasonal adjustment is a means of removing the estimated effects of normal seasonal variation and ‘trading day effects’. A ‘trading day effect’ reflects the varying amounts of activity on different days of the week and the different number of days of the week in any month (i.e. the number of Sundays, Mondays, etc.). Adjustment is also made for Easter which may affect the March and April estimates differently. Smoothing the seasonally adjusted series reduces the impact of the irregular component of the seasonally adjusted series and creates trend estimates. More information about these processes is available in the Information Paper: A Guide to Interpreting Time Series - Monitoring Trends: An Overview (cat. no. 1349.0) also linked above.
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