Statistical Data Revision Policy
Statistical Data
Revision Policy
June 2012
CONTENTS
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1. Introduction
The Data Revision Policy has been prepared based on the analysis of the need for interpretation of good practices in the statistical system and the need for the statistical system to increase users’ trust in the statistical data that are produced.
The Revision Policy describes the basic concepts of revision, the types of revisions, publication status, assessment for performing revision and documentation, communication and coordination of revisions.
The revision policy represents a global framework allowing every statistical area to create its own approach in accordance with the basic principles, while adhering to the recommendations contained in European Commission regulations pertaining to the relevant areas, the Compendium of Eurostat, as well as the standards of IMF and other international organisations. The policy is a framework that can be changed and supplemented in accordance with the changes in the statistical standards of Eurostat or other international organisations, i.e. statistical standards in general, and in connection with the changes in the data collection methods, data sources and coordination between participants in the statistical system.
2. Bases for prepapration of the Revision Policy
The bases for preparing the Revision Policy (hereinafter referred to as the “Policy”) are:
• Law on State Statistics , where Article 4 specifies the principles of the Code of Good
Practices, relating to confidentiality and quality of statistics.
•
Principle 2 of official statistics of the United Nations : "To retain trust in official statistics, the statistical agencies need to decide according to strictly professional considerations, including scientific principles and professional ethics, on the methods and procedures for the collection, processing, storage and presentation of statistical data" (www.stat.gov.mk)
•
European Statistics Code of Practice – principles 6, 8 and 12 (www.stat.gov.mk) ‐ principle 6 ‐
Indicator 6.6"For bigger revisions and changes in the methodologies information is providing at advance, principle 8 ‐ indicator 8.6 "revisions are making according the standards, good established and transparent procedures and principles', principle 12 ‐
Indicator 12.3"Revisiona are regularly analysed for improvements of the statistical processes"(www.stat.gov.mk)
•
Data quality assessment – generic framework (DQAF) of the IMF
− Principle 1 – Timeliness and integrity ‐ 1.2.4 "Advance notice is given of major changes in methodology, source data and statistical techniques";
− Principle 3 – Timeliness and reliability ‐ 3.5.1 "Studies and analyses of revisions are carried out internally", but "revisions are also made public"
− Principle 4- 4.3 "Revision policy is made available to users and the public"
•
Strategy of the State Statistical Office 2012 ‐ 2014 , section 1.3.1 Values and section 1.4
( www.stat.gov.m
к )
•
Dissemination Strategy 2010 ‐ 2012 “Strengthened confidence in official statistics” ‐ www.stat.gov.mk
•
Q uality Strategy of the State Statistical Office 2010 ‐ 2012 ‐ www.stat.gov.m
к
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3. Basic concepts
3.1 Definition of data revision
Data revision is an activity undertaken by authorised bearers of statistical surveys in order to modify already published data available to the public through statistical outputs in paper or electronic format, for the purpose of preparing data in accordance with new methodologies or applying new calculation methods that provide comparable data in accordance with international recommendations.
3.2 Types of revisions
3.2.1 Types of revisions in relation to planning
Revision planning is a process whereby discussions between participants in statistical survey implementation and analyses are used for planning the procedures and phases of revisions, the scope and the time frame for their implementation. With regard to this process, there are:
3.2.1.1 Planned revisions
Planned revisions are initiated by changes in classifications and changes in statistical methodologies, which in turn affect the importance and quality of data.
Planned revisions incorporate more complete data or data used for harmonising data from large ‐ scope surveys or censuses.
- Planned revision is also data revision for the purpose of preparing a new weighting structure of a previously defined period – every fifth year, every even ‐ numbered year, etc.
- Regarding monthly data, planned revision may be performed if there is a quarterly and/or annual survey in the same statistical area, which is used to harmonise the monthly data, as a regular procedure.
- Planned revision is also data preparation by using seasonal adjustment methods.
Planned revisions are published in the Five ‐ Year Programme and they are usually carried out no sooner than every 5 years.
3.2.1.2 Unplanned revisions
These revisions are usually not planned as part of the work process, but may be performed when changing data sources which after their analysis and evaluation are incorporated in the calculations, or are the result of changing some of the observation units because of their reclassification. Changes in administrative data sources or revision of data from other institutions can be reasons for unplanned revisions if they are not envisaged in the Five ‐ Year Programme as planned revisions.
Unplanned revisions are published in the Annual Work Programme of the State Statistical Office.
The explanations of such revisions are part of the methodological explanations of print and web editions.
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3.2.1.3 Combined revisions
Combined revisions occur when performing planned revisions of published data along with unplanned revisions due to changes in data sources or reclassification of units in the period between planned revisions. These revisions are usually large in scope and are announced in published editions, in the preface and in the methodological explanations.
3.2.2 Types of revisions in relation to their scope
The scope of the revision is related to the extent of the methodological changes that need to be implemented, the length of the time series for which data will be revised, and to the significance of the data for the economy and the society. Regarding the scope, there are:
3.2.2.1 Major revisions
These revisions are prepared when consistency needs to be ensured in terms of methodologies and classifications across multiple statistical areas, when new definitions and topics are implemented in accordance with international standards or when data are harmonised with census data. Due to the importance of these processes whereby already published data are modified, the decision for such activities is made by the Director of the State Statistical Office upon recommendation of the Executive Board. Major revisions are also planned revisions that are announced in the Five ‐ Year Programme and in the Preface of the latest published edition in the statistical area.
3.2.2.2 Minor revisions
These revisions of published data are usually performed when new data are received after the publication period in the specified time frame and which affect the value of published data, or when data with shorter periodicity (monthly and quarterly) are revised for the purpose of reconciliation with annual data. During such revisions, the methodological changes are insignificant.
This revision is announced in the methodological notes in the published edition in the statistical area.
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4. Publication status, assessment for performing the revision and documentation
4.1 Publication status
Revised data series are no less valuable than non ‐ revised ones. Doubt and criticism are common for both – transparency and openness to the users are crucial in both cases. For these reasons, when publishing data several statuses are used, as follows:
•
Preliminary data – marked with "P" in published materials
These are data published in accordance with international standards and with the Advance
Release Calendar, and are of great significance and interest for users. Such data can be monthly, quarterly and annual data. They are usually prepared without having obtained complete data, but statistically assessed as relevant and close to the expected definitive data. Preliminary data are usually published in T+1 month if monthly, T+1 quarter if quarterly, T+6 months if annual, and T+9 months for national accounts and structural statistics. For statistical areas where only final data are available this status is not published.
•
Definitive data – marked with "D" in published materials
These are data published after the completion of data from several available sources. After the data have been published as definitive, no corrections are made except in major revisions, but no more than three times. National accounts definitive data are published no later than two years after the reference period.
4.2 Assessment for data revision and documentation
4.2.1
Criteria for analysis of the need for revision
The following criteria are used for assessing the need for revision when reaching a decision:
•
Area of statistical data
For areas where data are published in absolute values, the revision is more significant compared to areas producing relative data that usually show trends, even though these data should also be revised in accordance with good practices.
• User interest for data from the respective area
Usually, for data which are sought after by users the need for revision is greater in order to provide quality information from the respective areas.
• Significance of data revision for the system of data from multiple areas.
When revising data that represent inputs in other calculations or when aggregate data need to be revised due to methodological changes, the extent of the influence of these revisions on the data system is thoroughly analysed, in order to determine the type of revision required.
4.2.2 Revision method
In order to ensure transparency of the revision procedure, a plan needs to be prepared, i.e. a document describing the revision procedure and containing information for assessment of the existing data sources and calculation methods, assessment of the quality of the new source and assessment of the method to be applied in the revision. Certain revisions implement completely new procedures in accordance with a certain regulation or recommendation; sometimes revisions are performed due to the inclusion of new units in the population, sometimes a decision can be made to apply a new disaggregation structure, etc. For this purpose, various methods are defined.
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In some revisions data calculation is made by reprocessing existing data, while in other revisions recalculation is made by applying certain coefficients, structures or models, depending on the available data and the possibility of obtaining new data. The methods must be announced to users in the methodological explanations of the editions containing the revised data. In addition to specifying the reasons for changing the calculation method, there must always be a comparative table of data before revision and revised data.
4.2.3 Period for which revision is performed and time of implementation
Of particular importance for the process of revision is the selection of the period for carrying out the revision and the period for which data are revised. The time when the revision is performed depends on the available human resources and the scope of the revision. The time period for which data are revised depends on the international recommendations for revision of the series and on the availability of data and data sources to be used in the revision. During major revisions, in order to obtain a comparable series of data, the period of revised data is usually no shorter than
5 years for annual data.
4.2.4 Documentation on revised data
When performing a major revision a new edition is prepared, titled “Revised data for the period
….. ‐ …..”, presenting revised data along with special tables and documentation – methodological explanations describing the data changes. This edition must also include a comparative table of previous and new data, and a special table presenting the changes in relative data.
During minor revisions the data changes are explained in the regular edition, and the methodological notes describe the reasons for the revision.
Revised data, after publication of the special edition with revised data, are integrated in the next edition of published materials for the respective areas, if they are part of a series.
Revised data in published materials are marked with "R" .
Revised data, if not pertaining to the entire data series when part of a larger series, in published materials are marked with "R" starting from the period when the revision was made. If the entire time series is revised, the marking "R" is inserted in the title, in the column of revised data.
The same rules apply for data published on the web site.
5. Communication and coordination of revisions
In order to maintain users’ trust, it is particularly important to have well ‐ defined activities for data revision. First of all, every data revision in the State Statistical Office must be known to
"everybody", i.e. all employees in the departments using the data. This is made possible by announcing minor revisions in the Annual Work Programme.
Major and planned revisions are announced in the Five ‐ Year Programme by all participants in the
Programme, for the purpose of ensuring mutual information between the State Statistical Office and other authorised bearers of statistical surveys, and for informing data users.
Exchange of information in the shorter term about unplanned revisions between the State
Statistical Office and other authorised bearers of statistical surveys should be made possible through cooperation and coordination.
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