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Evaluating Demetra +

The Time Series Analysis section (TSA) has recently completed a preliminary evaluation of Demetra+, seasonal adjustment software used and provided by the European Statistical System and free to download from the Internet. Demetra+ is one of the 'off the shelf' time series products thought to have a place in future ABS time series infrastructure. The preliminary evaluation was undertaken to assess initial broad suitability for incorporation into ABS time series functionality, and focussed on:

· ensuring the safety of the software being brought into ABS computing environment

· identification of problems with installation or analysis

· identification of special requirements with installation and user support

· assessing that the required functionality to perform seasonal adjustment comparable to the existing ABS time series system exists

· checking the stated capability of Demetra+ to perform seasonal adjustments on a whole set of time series

· confirming all available methods for importing data and metadata into Demetra+

· exploring methods and formats when exporting output out of Demetra+.

Findings from the preliminary evaluation have been promising. Demetra+ incorporates the two most popular seasonal adjustment methods: X-12-ARIMA from the United States Census Bureau and TRAMO/SEATS from the Bank of Spain. It provides TSA with an opportunity to explore the additional option of using a model based seasonal adjustment method in addition to its current moving average based approach when decomposing a time series. It also facilitates the comparability of the results and diagnostics from both methods.

During the remainder of the year, TSA staff are planning to perform further feasibility studies as well as an in-depth investigation into the utility of this tool for seasonal adjustment of ABS time series. Comparisons with existing seasonal adjustment infrastructure will also be made to identify any gaps or other differences in output and diagnostics that might arise. The focus is not only on Demetra+ functionality, but also how it will mesh with existing and emerging infrastructure.

Further Information
For more information, please contact Lujuan Chen (02 6252 6342 lujuan.chen@abs.gov.au)