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National Accounts Revisions Policy: updated
November 2020
In this section
1. Background
2. Annual reassessment
3. Quarterly data
4. Monthly data
5. Notification of revisions
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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
Associated statistical bulletins such as:
Business investment
UK trade
Index of Production
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Index of Services
Output in the construction industry
Consumer trends
Also 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 (PDF, 206KB) (http://www.ons.gov.uk/ons/guidemethod/revisions/revisions-policies-by-theme/economy/public-sector-accounts-revisionspolicy.pdf).
What is a revision?
A revision is a scheduled change to any published Office for National Statistics (ONS) output.
Examples of revisions could be the following.
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
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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
(https://www.statisticsauthority.gov.uk/code-of-practice/), 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 (https://www.statisticsauthority.gov.uk/publication/national-accountsoffice-for-national-statistics/).
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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 guide to
UK national accounts
(https://www.ons.gov.uk/economy/nationalaccounts/uksectoraccounts/methodologies/agui
detotheuknationalaccountsmarch2020). These main annual estimates are usually
incorporated into the national accounts around 18 months after the year they relate to. For
instance, results from the 2018 ABS were included in the 2020 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, in order 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 chainlinking”, is that volume series, expressed in currency terms, are revised most years as the
reference year to which they refer, is moved forward. The reference year normally moves on
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one year in line with the most recent supply and use balanced year. For example, in the
2020 Blue Book the reference year moved to 2018.
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 a number of significant
changes to the national accounts, which have resulted in major revisions outside the usual
period. For instance:
in 1998, the ONS introduced the European System of Accounts 1995 (ESA95)
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, which 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, the ONS introduced a new industrial classification, the Standard Industrial
Classification 2007 (SIC 2007), to the national accounts
in 2014, the ONS moved from ESA95 to the European System of Accounts 2010
(ESA2010)
in 2019, we introduced a new framework for the way we produce national accounts
(https://www.ons.gov.uk/economy/nationalaccounts/uksectoraccounts/articles/national
accountsarticles/anupdateofindicativeimpactsongdpcurrentpriceandchainedvolumeme
asureestimates1997to2016)
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
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Table 1 summarises the revisions policy for the next annual reassessment of data to be
published in September 2020.
Table 1: Revisions policy for the next annual reassessment of data
Year Current price data Chained volume measure data
Latest full year (2020
in Blue Book 2021)
Include latest data from short-term
sources.
Include updates to current prices and
deflators. Update reference year to 2019.
First results from
main inquiries (2019
in Blue Book 2021)
Include first results from ABS and
HMRC data.
Include updates to current prices and
deflators. Update reference year to 2019.
Updated results from
main inquiries (2017
and 2018 in Blue
Book 2020)
Include later results from annual
inquiries and ensure adjacent years
are consistent.
Include updates to current prices and
deflators. Update reference year to 2019.
Early years (2018 and
earlier in Blue Book
2020)
Only exceptional changes to data or
significant changes to methodology
or classifications taken on for these
periods .
Include updates to current prices and
deflators caused by methodology changes
and classification changes. Update
reference year to 2019.
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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 2020,
the period up to and including Quarter 4 (Oct to Dec) in 2018 will not be reassessed until
Blue Book 2021.
For periods from Quarter 1 (Jan to Mar) 2018 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.
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Table 2 summarises how revisions are planned to be incorporated over the quarterly cycle
for the 12 months commencing with the First quarterly estimate of GDP for Quarter 3 (July
to Sept) 2020.
Table 2: Revisions timetable for quarterly estimates of GDP
Month of publication First period being revised Publication
November 2020 Quarter 3 (July to Sept)
2020
GDP first quarterly estimate, UK: July to September
2020
December 2020 Quarter 1 (Jan to Mar)
2019
GDP quarterly national accounts, UK: July to
September 2020
February 2021 Quarter 1 (Jan to Mar)
2020
GDP first quarterly estimate, UK: October to
December 2020
March 2021 Quarter 1 (Jan to Mar)
2020
GDP quarterly national accounts, UK: October to
December 2020
May 2021 Quarter 1 (Jan to Mar)
2021
GDP first quarterly estimate, UK: January to March
2021
June 2021 Quarter 1 (Jan to Mar)
2021
GDP quarterly national accounts, UK: January to
March 2021
August 2021 Quarter 2 (Apr to Jun) 2021 GDP first quarterly estimate, UK: April to June 2021
September 2021 Fully open for revision GDP quarterly national accounts, UK: April to June
2021
Source: Office for National Statistics
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Monthly data
Monthly gross domestic product (GDP) publications will only revise previous months in the
quarter that the data refers 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).
The timetable for revisions of monthly GDP for the 12 months commencing with GDP
monthly estimate, UK: September 2020 is shown in Table 3.
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Table 3: Revisions timetable for monthly estimates of GDP
Month of publication First period being revised Publication
October 2020 Fully open for revision GDP monthly estimate, UK: August 2020
November 2020 July 2020 GDP monthly estimate, UK: September 2020
December 2020 No revisions GDP monthly estimate, UK: October 2020
January 2021 January 2019 GDP monthly estimate, UK: November 2020
February 2021 January 2020 GDP monthly estimate, UK: December 2020
March 2021 No revisions GDP monthly estimate, UK: January 2021
April 2021 January 2020 GDP monthly estimate, UK: February 2021
May 2021 January 2021 GDP monthly estimate, UK: March 2021
June 2021 No revisions GDP monthly estimate, UK: April 2021
July 2021 January 2020 GDP monthly estimate, UK: May 2021
August 2021 April 2021 GDP monthly estimate, UK: June 2021
September 2021 No revisions GDP monthly estimate, UK: July 2021
Source: Office for National Statistics
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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 will also contain tables that provide information to enable
users to put these revisions into an historical context. Revisions triangles supporting this
information are also published on the ONS website, to allow users to analyse past revisions
for themselves.
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