1. Background

The national accounts represent a wide array of data on areas as diverse as production, trade, earnings, spending, investment in fixed and financial assets and balance sheets. The nature of the integrated national accounts system is that all activity is linked, so a change in one area will have an impact elsewhere; consequently, making revisions to one part of the national accounts may lead to revisions throughout the system.

The main strength of the system is that it allows analysis of the various economic indicators both in isolation and in conjunction with others. The strength of the integrated national accounts system, however, may mean less flexibility for introducing revisions at any point in time. The National Accounts Revisions Policy is designed to give users a clear understanding of the time periods that could see revisions at each data release and why incorporating revisions from a single source is not a simple matter.

Outputs covered

The National Accounts Revisions Policy covers all published quarterly and annual series within the UK National Accounts. This includes all the series that appear in the following statistical bulletins:

  • GDP monthly estimate

  • GDP first quarterly estimate

  • Quarterly national accounts

  • Quarterly sector accounts

  • Balance of payments

It includes associated statistical bulletins such as:

  • Business investment

  • UK trade

  • Index of Production

  • Index of Services

  • Construction output in Great Britain

  • Consumer trends

It also includes the core national accounts publications:

  • UK National Accounts, The Blue Book

  • UK Balance of Payments, The Pink Book

  • UK Economic Accounts

  • Regional accounts

  • Welsh short-term indicators

Although using national accounts concepts, the Public sector finances statistical bulletin has adopted a different revisions policy.

What is a revision?

A revision is a scheduled change to any published Office for National Statistics (ONS) output. Examples of revisions could be:

Updates to incorporate better or more complete source data such as:

  • more accurate reporting by respondents

  • source data that more closely match the concepts

  • availability of late or more comprehensive data

Updates to capture routine recalculations, such as:

  • incorporation of updated seasonal factors

  • benchmarking

Improvements to methods or systems, such as:

  • changes in statistical methods

  • changes in concepts, definitions and classifications

  • updating of the base period

A correction is an unplanned revision to any published ONS output due to the identification of an error. Where an error has been identified but a decision is taken to postpone correction until the next regular release in line with the Code of Practice for Statistics, this will be transparently explained. Changes as a result of a correction will be clearly labelled as a correction rather than a revision. Further details regarding this practice are available on the UK Statistics Authority website.

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2. Annual reassessment

One of the main principles for compiling UK National Accounts is that our main annual sources provide the best quality and most comprehensive data. The most significant of these sources are the Office for National Statistics (ONS) Annual Business Survey (ABS) and Her Majesty’s Revenue and Customs (HMRC) earnings estimates. These sources provide the core inputs to estimating the level of gross domestic product (GDP) through the supply and use framework. This framework provides the basis for confronting a wide range of source data and for balancing the three different approaches to compiling GDP, as well as many of the main components of the sector accounts.

Further information on all three approaches to measuring GDP can be found in the short guide to national accounts (PDF, 317KB). These important annual estimates are usually incorporated into the national accounts around 18 months after the year they relate to. For instance, results from the 2016 ABS were included in the 2018 Blue Book. Estimates for later periods are taken forward from this point using a wide range of shorter-term sources.

Once the figures from these major sources have been incorporated into the national accounts, there should be no need to revisit the period to which they relate during subsequent quarterly rounds. Typically, data from these major sources will be revisited when the next set of annual results are available, to incorporate any late returns from the previous year and to ensure consistency between consecutive years. Following the second supply and use balance for any given year, most of the data will be close to final and only exceptional changes that lead to significant revisions will be considered in subsequent periods.

Annual chain linking

A consequence of one of our annual methodological updates, known as “annual chain linking”, is that volume series, expressed in currency terms, are revised each year as the reference year to which they refer is moved forward. Each year, the reference year moves on one year in line with the most recently supply and use balanced year. For example, in the 2018 Blue Book, chained volume measures were re-referenced to 2016 from 2015 in the previous Blue Book.

Other sources of revisions

Other changes due to methodology, concepts or classifications can lead to revisions after the source data have been finalised. In recent years there have been several significant changes to the national accounts, which have resulted in major revisions outside the usual period. For instance:

  • in 1998, ONS introduced the European System of Accounts 1995: ESA 1995

  • in 2001, the national accounts incorporated the results from the new Annual Business Inquiry (former name of the ABS) as well as significant improvements to the Business Register that underpins ONS surveys

  • in 2003, annual chain linking was introduced alongside significant improvements to price deflators for gross fixed capital formation and imports of goods

  • in 2011, ONS introduced a new industrial classification, the Standard Industrial Classification 2007: SIC 2007, to the national accounts

  • in 2014, ONS moved from ESA 1995 to the European System of Accounts 2010: ESA 2010

It is impossible to introduce major developments and improvements in the national accounts without making revisions, therefore, these changes have led to revisions throughout the time series.

Revisions policy for the next annual assessment

Table 1 summarises the revisions policy for the next annual reassessment of data to be published in Summer 2019.

An article was published on 11 October 2018, describing the planned scope and content of the publications due to be published in September and October 2019.

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3. Quarterly data

Periods covered by the main annual sources are not reopened until the next annual reassessment, apart from in exceptional circumstances. For instance, after Blue Book 2018, the period up to and including Quarter 4 (Oct to Dec) in 2016 will not be reassessed until Blue Book 2019.

For periods from Quarter 1 (Jan to Mar) 2017 to the latest period, the quarterly process of updating the national accounts is based on a monthly cycle affecting particularly gross domestic product (GDP) estimates. This cycle is linked notably to the monthly Index of Production, Index of Services, retail sales and trade estimates. During each quarter, national accounts estimates are published, as follows, in the weeks after the end of the quarter:

  • around six weeks: a first quarterly estimate of GDP with an output, expenditure and income breakdown

  • around 12 to 13 weeks: full quarterly national accounts, including a further update of GDP, balance of payments and sector accounts

Generally, quarters earlier than the latest quarter are only revised during the second of these releases. The focus of the earlier releases is to provide the best estimate of quarterly growth in the most recent period. However, an exception is made in February where the first estimate of the latest full calendar year becomes available and it is helpful to ensure that seasonally adjusted data are in line with the unadjusted data across the whole year. At the second release of each quarter, it is possible to provide a complete set of accounts for the quarter and to take account of revisions to the component items for earlier quarters.

Value Added Tax (VAT) turnover data will be incorporated into estimates of GDP in each quarterly national accounts release. VAT turnover data are not available in time for inclusion in the same time period as GDP releases, therefore there will always be a lag in the implementation of VAT turnover data of three months. The period for which VAT turnover are used will be detailed in the Quarterly national accounts statistical bulletin.

Table 2 summarises how revisions are planned to be incorporated over the quarterly cycle for the 14 months commencing with the first quarterly estimate of GDP for Quarter 2 (Apr to June) 2018.

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4. Monthly data

Monthly gross domestic product (GDP) publications will only revise previous months in the quarter that the data refer to (the reference period). It should be noted that, in the month in which monthly GDP and the first estimate of quarterly GDP are published, their revisions period will also coincide.

The revisions policy for Index of Services, Index of Production and Index of Construction will mirror that of monthly GDP. They will “catch up” on revisions resulting from the use of Value Added Tax (VAT) data published in the previous quarterly GDP release in the subsequent monthly release.

Additionally, there are three revision categories that take on revisions from a longer period of time; annual benchmarking, seasonal adjustment, and UK National Accounts, The Blue Book. All these categories occur on a yearly basis. Annual benchmarking takes on revisions from the beginning of the previous calendar year. In the case of seasonal adjustment, at the point in which the full year is formed for the first time, the period is open for revision to allow for seasonal factor changes to be updated. Blue Book releases are open to revisions for the period back to 1997 (the earliest point for which data are available).

Table 3 shows the timetable for revisions of monthly GDP for the 15 months commencing with GDP monthly estimate, UK: June 2018.

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5. Notification of revisions

The scope of future planned revisions is regularly announced in advance of the annual reassessment of data. These announcements are made in the form of articles on the Office for National Statistics (ONS) website, which describe the nature of any revisions that are planned outside of the regular process.

Exceptional causes of revisions, such as changes to the industrial classification or international accounting standards, will be accompanied by a dedicated communication plan, which might consist of a series of articles and seminars on concepts, methodology and probable effects. This was relevant in Blue Book 2014 when the European System of Accounts 2010: ESA 2010 was implemented across Europe.

Revisions to the main series presented within national accounts statistical bulletins are published in tables. The bulletin Quality and methodology section will also contain tables that provide information to enable users to put these revisions into a historical context. Revisions triangles supporting this information are also published on the National Statistics website, to allow users to analyse past revisions for themselves.

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