ESS guidelines on seasonal adjustment : 2015 edition

The establishment of common guidelines for seasonal adjustment (SA) within the European Statistical System (ESS) is an essential step towards a better harmonisation and comparability of infra-annual statistics, especially Principal European Economic Indicators (PEEIs). The ESS Guidelines on Seasonal Adjustment address the need for harmonisation expressed on several occasions by many users such as the European Central Bank (ECB), European Commission services, and the ECOFIN Council. The definition of best practices in the field of seasonal adjustment has been long debated at European level. Since 2007, the Seasonal Adjustment Steering Group co-chaired by Eurostat and the ECB gave a new and crucial input to the compilation of the first edition of the guidelines, published in 2009. The first edition has been widely accepted and implemented. However, taking into account the experience accumulated since 2009 and the need to further clarify some specific aspects, in 2012 the Seasonal Adjustment Steering Group decided to launch a revision of the guidelines. The ESS Guidelines on Seasonal Adjustment are the outcome of the revision work and the ESS Committee (ESSC) endorsed them in November 2014. The revised ESS Guidelines on Seasonal Adjustment present both theoretical aspects and practical implementation issues in a friendly and easy to read framework, thereby addressing both experts and nonexperts in seasonal adjustment. They meet the requirement of principle 7 (Sound Methodology) of the European Statistics Code of Practice and their implementation will also be in line with principles 14 (Coherence and Comparability) and 15 (Accessibility and Clarity). The guidelines also foster the transparency of seasonal adjustment practices by encouraging the documentation of all seasonal adjustment steps and the dissemination of seasonal adjustment practices by means of the metadata template for seasonal adjustment. Finally they allow for development of expertise and capacity building. The revised version of the guidelines includes a new section with a policy for seasonal adjustment, making the revised version of the guidelines consistent with the guidelines on revisions policies. It also better describes the different steps in seasonal adjustment. Finally the specification of alternatives has been reviewed, making them more operational. This major achievement has been possible thanks to the commitment of a wide range of well-known experts on seasonal adjustment.