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Harmonisation of Seasonal Adjustment Methods in EU and OECD Countries. Ronny Nilsson Statistics Directorate. Contents. Background Results of EU and OECD Surveys on SA - IT approach (EU survey) - Methodology (EU and OECD surveys) Future work. Background.
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Harmonisation of Seasonal Adjustment Methods in EU and OECD Countries RonnyNilsson Statistics Directorate
Contents • Background • Results of EU and OECD Surveys on SA - IT approach (EU survey) - Methodology (EU and OECD surveys) • Future work
Background • Monitor Euroland with early national data and facilitate comparison with other economies • Software development for SA - DEMETRA • Task Force, SA Co-ordination Group (CMFB) with a mandate - harmonisation of SA in EU: - integration of X-12 ARIMA and Tramo/Seats - use of DEMETRA by NSI and NCB
Results of EU Survey Main conclusions: • X-12-ARIMA and Tramo/Seats only relevant methods • Separation between research/production level • Program version policy is urgent • Integration of the two SA methods is important but not urgent • DEMETRA can not fulfil the role of a standard
Priorities for harmonisation of SA procedures in EU countries • Use of single SA software integrating both X-12 ARIMA and Tramo/Seats • A single reference source code underlying the SA software (statistical and technological) • Standardisation of the reporting of SA metadata, in particular quality aspects • Definition of best SA practices via the European network of expertise
Results of EU- OECD surveys Survey characteristics EU countries + Norway • Sample:16 NSIs inc. Eurostat,17 NCBs inc. ECB • Response rate: 94% for NSIs, 76% for NCBs OECD non-EU countries (15 countries) • Sample: 15 NSIs 15 NCBs and 5 other instit. • Response rate: 93% for NSIs, 50% for NCBs and 80% for other institutions
SA Methods: To day (%) TS X-11 X-12 TS/X-12 Other EU 19 50 0 23 8 Non-EU 0 43 35 13 9 OECD 10 47 16 19 8 • OECD: X-11 dominates the market • EU: TS in stand alone mode is widely used • Non-EU: X-11 and X-12 used by some 80%
SA Methods: In the future (%) TS X-11 X-12 TS/X-12 Other EU 24 0 28 40 8 Non-EU 22 6 44 17 11 OECD 24 2 35 30 9 • OECD: X-12 and TS/X-12 in combination will be the two main methods • EU: TS/X-12 in combination will dominate • Non-EU: X-12 will be the main method
Methods: Selection Process • Others: SEAABS, BV4, TESS, GLAS, STAMP • Selection of one or several methods on: - internal decision based on testing and evaluation phase (58 %) - historical reasons or recommendations (60 %) • Multiple methods are used because of: - possibility of cross checking results - specific features of each method
SA Diagnostics Satisfaction level • EU countries: 88 %, Non-EU countries 95 % • OECD countries: 90 % Main indicators/diagnosticsused: • Graphical Inspection (81 %) • Result/Analytical Tables (79 %) • Diagnostic test for ARIMA models (75 %)
Pre-adjustment features First priority: • Outliers detection and T-day correction/flow vari. Second priority: • Implementing national holidays • missing obs. and forecast test for model type Third priority: • Level shifts, additive outliers, seasonal breaks, Easter effect, user defined/dummy variables
Direct vs Indirect adjustment EU countries: • Aggregation problem considered by 30 %, but no method is predominant Non-EU countries: • Direct method is the most common method (58 %) • Indirect method is only used in large scale in the United States and Korea
Proj. factors vs Concurrent adj. EU countries: • 25 % of the institutions are considering the two methods, but no one is predominant Non-EU countries: • Projected seasonal factors are used by 63 % of the institutions as the regular method • Concurrent adjustment is used by 32 % on a regular basis
Update or Revision Policy Seasonal adjustment options: • fixed periodicity (Yearly) EU 58 %, Non-EU 80 % • afterrevisions in dataEU 30 %, Non-EU 36 % Model parameters: • fixed periodicity, EU no dominant pattern, but 60 % uses a yearly pattern in Non-EU • for selection of fixed filters and ARIMA models a yearly periodicity is predominant
Metadata and Publication Policy • Metadata on SA Method, SA Parameters and Working/trading day adjustment are stored by 85 % in the production database for internal usage • Only metadata on SA Method and Working/tradingday adjustment are stored by about 40 % in the dissemination database for external usage • Info on outliers is stored by 40 % and other types of metadata by 20 % of the institutions
Future Work • A merge of X-12 ARIMA and Tramo/Seats would be welcomed by most institutions using both methods, EU and OECD support this development • Eurostat proposal for a Reorganisation of SA Activities in the European Statistical System (ESS) - Steering Group (financial/human input) - User Group (evaluation/proposals) - Scientific Group (research and assessment)
Future Work • OECD Expert Group on “Short term Statistics” - Harmonisation of SA methods across OECD countries - link to EU Activities - Metadata and publication policy of SA for external users - Presentation of data; seasonally adjusted data vs trend-cycle (smoothed) data