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Accuracy and reliability

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National Accounts, Economic Statistics
Michael Berg Rasmussen
+45 39 17 37 68

mbr@dst.dk

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Water and Waste Water

The coverage of data abstraction water is assessed to be high. However, for fish farming the information may be insufficient. Therefore missing values have been imputed.

The coverage of data on waste water discharge is assessed to be high, as the information by law has to be included in development water management plans.

The coverage of data on abstraction of water, flows and deliveries to end users is assumed to be high.

The distribution on industrial groups - especially the 117 level - is subjected to some uncertainty.

Overall accuracy

The overall uncertainty has not been subjected to a quantitative assessment.

The coverage of the data concerning abstraction of water, flows in the water supply system and discharge of waste water is assumed to be high, subject to delayed or incorrect reporting by the users. Obvious errors are corrected in dialogue with the administrators of the databases.

The distribution on industrial groups - especially the 117 level - is subjected to some uncertainty.

Sampling error

Not relevant for these statistics.

Non-sampling error

The source data in both Jupiter and PULS databases contain measurement errors. They are not all identified in the data validation. It may be typing errors, errors in the units, missing reporting or reporting in wrong fields. The latest years may be underestimated due to late reporting.

Quality management

Statistics Denmark follows the recommendations on organisation and management of quality given in the Code of Practice for European Statistics (CoP) and the implementation guidelines given in the Quality Assurance Framework of the European Statistical System (QAF). A Working Group on Quality and a central quality assurance function have been established to continuously carry through control of products and processes.

Quality assurance

Statistics Denmark follows the principles in the Code of Practice for European Statistics (CoP) and uses the Quality Assurance Framework of the European Statistical System (QAF) for the implementation of the principles. This involves continuous decentralized and central control of products and processes based on documentation following international standards. The central quality assurance function reports to the Working Group on Quality. Reports include suggestions for improvement that are assessed, decided and subsequently implemented.

Quality assessment

The coverage of the data concerning abstraction of water, flows in the water supply system and discharge of waste water is assumed to be high, subject to delayed or incorrect reporting by the users. Obvious errors are corrected in dialogue with the administrators of the databases.

The distribution in industrial groups can be subject to uncertainty. The information on reimbursement water tax for companies and institutions subject to VAT is assumed to be complete. The information on floor space from the BBR (Danish Building and Housing Register) is found not to be complete for all the relevant public institutions. The number of employees has therefore been included in the estimates. No overall information on water content in products, evaporation of water from processes etc. is available from the recent years. Therefore the report Vandforbrug i fremstillingsindustrien (Water consumption in the industry; Environmental Project no. 259 from 1994) supplemented with up to date company specific information.

Data revision - policy

Statistics Denmark revises published figures in accordance with the Revision Policy for Statistics Denmark. The common procedures and principles of the Revision Policy are for some statistics supplemented by a specific revision practice.

Data revision practice

The water accounts are continuously improved when new data sources are available. Data series for e.g. water extraction or water consumption are completed if it can be validated by activity in the specific companies.