REVISIONS IN QUARTERLY GDP OF OECD COUNTRIES MEETING OF THE WORKING PARTY ON NATIONAL ACCOUNTS Paris, 10-12 October 2006 REVISIONS IN QUARTERLY GDP OF OECD COUNTRIES

Aims of the paper Building, maintaining and using revisions databases: the QNA-MEI experience Some remarks on strategy and tools for revisions analysis Size of revisions to the first published estimates (P) on MEI (May 1995 – Aug 2005)

Main Results Revisions between three years later estimates (Y3) and the first published estimates (P) of q-o-q GDP growth rates (%) on MEI. Mean absolute revision (1995.1-2002.4)* * BEL: 96.4;2002.4, DEU: 95.2.2002.4, PRT: 1996.1.2002.4, KOR 1999.4 2002.4.

Main Results Revisions between three years later estimates (Y3) and the first published estimates (P) of q-o-q GDP growth rates (%) on MEI. Relative mean absolute revision (1995.1-2002.4)* * BEL: 96.4;2002.4, DEU: 95.2.2002.4, PRT: 1997.1-2002.4, KOR 1999.4 2002.4.

Main Results Comparison between previous year’s and this year’s updated results of revisions of the 3 years later published estimates to the first published estimates (Y3_P) of q-o-q GDP growth rates (%) on MEI. Mean absolute revision. KOR: cannot be compared because last year data for Korea was not relevant.

The QNA-MEI revisions dataset OECD-ONS workshop on “Assessing and improving statistical quality. Revision analysis for the national accounts”, 7-8 October 2004 “The OECD also agreed to explore the possibility to expand and maintain the revisions database that was set up for purposes discussed in the workshop. An international dataset and the resulting summary measures of revisions should help to put countries’ individual revision analyses into an international context.” First elements presented also at the STESEG meeting, 27-28 June 2005

MEI as a revisions database source MEI monthly snapshots in principle provide historical data on subsequent releases on a wide range of key variables Provides a coherent set of variables representing the ‘information set’ available at successive monthly intervals MEI has been published as a CD Rom for many years

OECD interest in a revisions database Analysis – Are revisions random (i.e. centred around 0)? Are they in general becoming smaller? Support internationally coordinated research work to improve the quality of early estimation methods Encourage transparency in the statistical process

The QNA-MEI revisions dataset Initial OECD work (Ahmad, Bournot & Koechlin, 2004) was for G7 countries, period 1996 – 2000 Current project (Di Fonzo, STESEG 2005) Expand coverage to all OECD countries Expand time period covered Devise a scheme which can support ongoing production of real time database & summary revision analysis indicators Quarterly GDP and its components

Data availability for GDP (constant prices, sa) in the QNA-MEI revisions database MEI editions Vintages Countries First Last # May-95 May-06 95q1 06q1 133 1: USA 94q4 05q4 13: AUS, CAN, CHE, DNK, ESP, FIN, FRA, GBR, ITA, JPN, NLD, NOR, NZL Nov-95 95q2 127 1: DEU Nov-96 95q4 115 1: PRT Mar-97 96q3 111 1: BEL Mar-00 99q3 75 1: KOR Oct-03 03q2 32 1: CZE* Nov-03 31 1: AUT* Apr-04 03q4 26 1: GRC Nov-04 04q2 19 1: IRL Jul-05 05q1 11 1: HUN Sep-00 00q2 65 2: SWE, TUR 00q1 1: MEX Oct-05 8 1: SVK --- 3: ISL, LUX, POL

QNA-MEI revisions dataset Caveats for international comparisons P are not necessarily flash estimates Timeliness of P differs between countries No attempt is made to isolate the different types of revisions, (including errors) Differences may exist between estimates and national estimates No investigation into influence of economic cycle Period covers SNA93 introduction and other changes, fixed base, chain-linking

Release time of GDP (P) on MEI Further cautionary notes MEI is commonly published during the first week of the month Different release timing across countries There is no guarantee that the first number published in MEI is really the first number ever released ‘QNA-MEI view’ on timeliness in the release of GDP The true timeliness is ‘filtered’ through the publication practices adopted by OECD in the last decade

Revisions analysis: Summary statistics Mean revision Mean absolute revision Mean squared revision % L > P % sign(L) = sign(P)

Elements for discussion Presentation of revisions, evaluating the first revision registered on MEI, effect of different time periods on the summary statistics, stability of the results, use of other (simple) descriptive measures? Possible use of a QNA-MEI revisions database by member countries? Priority for analyzing other QNA series and how to use the results? - e.g. as an input to internationally coordinated methodological work? - To reconsider policies for communicating information on revisions to users?

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