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Revisions Analysis at Statistics Canada

Revisions Analysis at Statistics Canada. October 10, 2008. 2003-4 CSNA RP Toolkit. Why Study Revisions?. Statistical users and providers are both concerned about data quality. Main dimensions of quality: relevance, coherence, timeliness, accuracy and reliability.

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Revisions Analysis at Statistics Canada

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  1. Revisions Analysis at Statistics Canada October 10, 2008

  2. 2003-4 CSNA RP Toolkit Why Study Revisions? • Statistical users and providers are both concerned about data quality. • Main dimensions of quality: relevance, coherence, timeliness, accuracy and reliability. • Preliminary estimates are provided primarily for timeliness, while final estimates are deemed to be accurate or the most accurate possible. • As well as being timely, preliminary estimates should be reliable or are close approximates of final estimates. • Revision studies aim to measure the reliability of the preliminary (and intermediate) estimates. The focus is on revision patterns and their change over time. 3 Statistics Canada • Statistique Canada

  3. 2003-4 CSNA RP Toolkit TYPES OF REVISION Revisions can be classified by reasons or by timing • Reasons • Incorporation of better source data • Routine recalculation • Improvements • Correction of errors • Timing • Current revisions • Annual revisions • Historical (or comprehensive, major or benchmark) revisions More details: Carson, C.S., Khawaja, S. and Morrison, T.K. Revisions Policy for Official Statistics: A Matter of Governance. Sixteenth Meeting of the International Monetary Fund Committee on Balance of Payments Statistics, Washington D.C., December 1-5, 2003. BOPCOM-03/3A, pp 5-8. 7 Statistics Canada • Statistique Canada

  4. 2003-4 CSNA RP Toolkit FORMS OF REVISION STUDIES Revision studies at Statistics Canada have taken the following forms: • Study on levels or growth rates • Comparison between ranges of time periods (e.g. decades) • Component profiles and impact of sub-aggregates • Time profiles (different vintages) • International comparisons • Review of source data and estimation methods 8 Statistics Canada • Statistique Canada

  5. RP0304 QUARTERLY GDP REVISION SCHEDULE Statistics Canada • Statistique Canada 5

  6. RP0304 QUARTERLY GDP REVISION SCHEDULE REVISIONS IN THE PRELIMINARY YEAR PICK UP LATE SURVEY RETURNS AND RE-ESTIMATIONS AND UP DATES TO SEASONAL FACTORS Statistics Canada • Statistique Canada 5

  7. RP0304 QUARTERLY GDP REVISION SCHEDULE REVISIONS IN YEAR T+1 ARE LEVEL REVISIONS RELATED TO BENCHMARK LEVELS FOR THREE YEARS EARLIER – FEW NEW GROWTH RATE INDICATORS ARE AVAILABLE BUT SEASONAL FACTORS ARE UPDATED Statistics Canada • Statistique Canada 5

  8. RP0304 QUARTERLY GDP REVISION SCHEDULE REVISIONS TWO YEARS LATER INCLUDE EARLY BENCHMARK INFORMATION FOR WAGES AND SALARIES FROM T4 AND THE CAPITAL EXPENDITURE SURVEY Statistics Canada • Statistique Canada 5

  9. RP0304 QUARTERLY GDP REVISION SCHEDULE REVISIONS IN YEAR THREE REFLECT A FULL BENCHMARKING TO INPUT OUTPUT TABLES USING A FULL SET OF ANNUAL SURVEYS COVERING THE ENTIRE ECONOMY Statistics Canada • Statistique Canada 5

  10. RP0304 QUARTERLY GDP REVISION SCHEDULE REVISIONS IN YEAR FOUR ARE CONSIDERED « FINAL » - DETAILLED SOURCE DATA ON HEALTH AND EDUCATION SECTORS BECOME AVAILABLE Statistics Canada • Statistique Canada 5

  11. Third Quarter 1969 Shift from 90-day lag for release to 60 day lag First Quarter 1986 Adoption of GDP over GNP as feature estimate Full integration of quarterly accounts with annual Input Output Tables Significant Statistical Revisions Third Quater 1997 Conceptual Revision to SNA 1993 First Quarter 2000 Adoption of Fisher Formula for calculation of GDP First Quarter 2001 Capitalization of Software Statistical Events related to Revision Patterns Statistics Canada • Statistique Canada

  12. Other Significant events Various rebase exercises to Laspeyres-based real GDP Re-design of business survey strategies (1981 to 1989) Introduction of Provincial IO Program and overhaul of Annual Survey System (1999 to 2002) Agressive adoption of administrative data to reduce response burden (2003 – 2007) Next Historical Revision 2012/2013 Statistical Events related to Revision Patterns Statistics Canada • Statistique Canada

  13. Pre and post timeliness change 1969 Post adoption of SNA 1993 – in 1997 Recent revision patterns – 2001 to date Overview of revisions analyses Statistics Canada • Statistique Canada

  14. Pre and Post Timeliness Change Statistics Canada • Statistique Canada

  15. RP0304 Revision Study of seasonally adjusted quarterly real GDP, 1981 to 2003 After adoption of SNA 1993 • GDP growth rate - constant price, seasonally adjusted, quarter-on-quarter • Total revisions, incremental and cumulative revisions at each vintage (preliminary; 1Q, 1Y, 2Y, 3Y and 4Y later) • Revisions due to base-year, concepts-sources-method changes; historical revision • Revisions in the 1980s versus those in the 1990s • Revisions and the economic cycle Statistics Canada • Statistique Canada 4

  16. RP0304 GROWTH RATES - DIFFERENT VINTAGES Statistics Canada • Statistique Canada 12

  17. 2003-4 CSNA RP Toolkit PRELIMINARY & FINAL ESTIMATES & TOTAL REVISIONS Quarterly GDP Growth Rates and Total Revisions, 1981 to 1999 Seasonally adjusted, constant price, quarter-on-quarter, % point Statistics Canada • Statistique Canada 11

  18. Statistical Analysis BIAS & DISPERSION 2003-4 CSNA RP Toolkit Quarterly GDP Growth Rates and Total Revisions, 1981 to 1999 Seasonally adjusted, constant price, quarter-on-quarter, % point Statistics Canada • Statistique Canada 13

  19. RP0304 INCREMENTAL REVISIONS @ DIFFERENT VINTAGES 2003-4 CSNA RP Toolkit Statistics Canada • Statistique Canada 12

  20. 2003-4 CSNA RP Toolkit DISTRIBUTION OF THE REVISIONS “NORMAL”? 14 Statistics Canada • Statistique Canada

  21. RP0304 ECONOMIC EXPANSION AND CONTRACTION Statistics Canada • Statistique Canada 20

  22. 2003-4 CSNA RP Toolkit REGRESSION AND CORRELATION Statistics Canada • Statistique Canada 15

  23. 2003-4 CSNA RP Toolkit IMPACT OF SUB-AGGREGATES EXPENDITURE SIDE Statistics Canada • Statistique Canada 18

  24. RP0304 Revisions of quarterly real GDP(SAAR), 1981-2003 KEY FINDINGS • Marginally significant negative bias (0.1 percentage point) • The estimates were revised upwards more often than otherwise (52% of the time versus 38%) • A persistent run of positive revisions in 2nd half of 1990s (13 out of 15 revisions) • Evidence of lower dispersion measures. Mean absolute revision was reduced by 21.4% from 1980s to 1990s, but relative dispersion only dropped by 4.4%. • Preliminary IO benchmarks @ ‘3-years-later’ were the source of the largest shares of total revisions (over 50% on average) • Base-year and CSM changes had minor effect on revisions Statistics Canada • Statistique Canada 7

  25. RP0304 Revisions of quarterly real GDP(SAAR), 1981-2003 KEY FINDINGS • Preliminary and intermediate GDP growth rates estimates correctly indicated the sign (direction) of economic growth 95% of the time • Accelerations or decelerations were correctly identified two thirds of the time • Near-trend rates were correctly measured by different vintages 66% to 89% of the time. • Troughs were correctly indicated by all vintages, only one peak was missed by the preliminary series and one was missed by the two-year-later series. Statistics Canada • Statistique Canada 8

  26. Recent Revision Patterns Statistics Canada • Statistique Canada

  27. Recent Revision Analysis Statistics Canada • Statistique Canada

  28. Recent Revision Analysis Statistics Canada • Statistique Canada

  29. Recent Revision Analysis Statistics Canada • Statistique Canada

  30. Revisions Analysis is essential to a statistical process for determining areas for improvement Revision statistics need to be interpreted in the context of changes to the statistical system Source data improvements Conceptual changes Economic changes How should STC improve communications of revisions? Link, break or re-estimate? Historical revisions – « Big Bang » or Staged Questions? Conclusions and questions for discussion Statistics Canada • Statistique Canada

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