207. The process for giving advice to users, including policy-makers, about likely revisions is governed by the National Statistics Code of Practice and Protocols, in particular the Protocols on Release Practices and Revisions. Although the Protocols were only issued relatively recently, many of the practices laid down in them are longstanding. Users are fully familiar with them and this affects the guidance they seek in advance about likely revisions. The answer to this question also needs to be seen in the context of the almost continuous contact between the ONS and Treasury and Bank on the latest data and issues arising (see also the answer to G.2).

208. Key provisions in the Release Practices Protocol are that:

• statistics will be released as soon as practicable once they ... are judged fit for purpose;

• National Statistics should be made equally available to all, at the same time;

• planned methodology changes will be notified at least one release period earlier.

• For all recurring releases, back data will be released at least by the time of the

209. The effect of the Protocols is that in general users do not get, and do not expect to get, advice in advance about the vast majority of specific revisions, i.e. those due to the receipt of fuller information. (Indeed given the requirement to publish statistics as soon as practicable once they have been deemed fit for purpose, the ONS itself does not get much advance notice.) However, it is common practice when preliminary estimates are published to advise users that data are likely to be revised on receipt of later information. On occasion warnings are given about particular factors increasing the risk of revision, for example the introduction of a new Customs and Excise computer system.

210. There are, however, a number of exceptions and qualifications to the situation described above, and the position in respect of revisions due to methodological changes is different.

211. The exceptions relate to the provision of information to key policy-makers in the Treasury and Bank of England:

• under the Release Practices Protocol the responsible ministers and a limited number of officials get privileged early access, 40.5 hours for market sensitive statistics; this applies to all relevant First Releases whether or not there are revisions; and while privileged early access is so that ministers “can respond completely when questions arise at the time of release”, it also allows them to take account of any policy implications;

• this early access is also given to the Governor of the Bank of England, who, with

the agreement of the National Statistician, may extend it to members of the Monetary Policy Committee and officials advising it when the Committee is meeting to decide the appropriate level of interest rates;

• exceptional arrangements are also made for the Budget; once the date of the Pre-Budget Report or Budget itself is announced, the publication timetable for releases is re-examined and early access to certain data may be given to a limited number of Treasury officials;

• finally the Protocol on Consultation with Ministers says that, when potential

changes impinge on policy the National Statistician should consult ministers at “an early stage” and “should indicate, where possible, the impact on published series .... well before any changes are implemented”. This provision was invoked in the case of revisions to imports due to VAT fraud.

212. Rather more guidance is possible in the case of methodological changes. Major methodological changes are always fully explained in advance through seminars and articles. During 2003 there were for example extensive discussions between the ONS, Treasury and Bank on the introduction of annual chainlinking in the National Accounts, the effect of VAT fraud on imports and methodological changes to retail sales. Where possible some indication is given about the sign and


Responses to NIESR Questions


213. The other source of guidance on likely revisions is from analysis of past revisions. ONS publishes articles analysing revisions to GDP and its expenditure components on a regular basis. Such analyses cover revisions from all sources. It is planned to extend this practice by including details of past revisions in all ONS First Releases of economic time series by the middle of 2004.

214. As a result of this body of material key users are aware that revisions are a natural part of the statistical process. For example the Bank of England stated in its August 2003 Inflation Report that “the MPC takes account of the likelihood that GDP

data will be revised when deciding how much weight to put on the latest data”.

215. In the past the Treasury and ONS have agreed performance targets for revisions to key economic statistics. Initially these were drawn up in 1991 as part of the targets by which ONS’s performance as a Next Steps Agency was monitored. The revisions targets were later subsumed into the Service Level Agreement between the ONS and Treasury agreed in 1998. The targets are, however, no longer operative as it was agreed that the need for them had been overtaken by the National

Statistics Code of Practice and Protocols, particularly the Protocol on Revisions which sets out procedures by which revisions are communicated. There was also concern that the targets might have perverse incentive effects for ONS.

216. To sum up, users do not seek advance advice on normal revisions, i.e. those due to later information. This is neither practical nor consistent with the National Statistics Code of Practice. On the other hand there is an active dialogue on revisions expected as a result of planned methodological changes.

In document "Last quarter’s GDP growth rate revised up by O 3pp": a typical revision? (Page 80-82)