Accuracy and reliability

Overall accuracy

The uncertainty levels of the two main sources for the statistics differ.

Extrastat covering trade with non-EU countries is generally of a high quality. However, the reliability of the figures at the detailed level is affected by:

• The figures on imports probably have a slightly higher quality compared to the figures on exports, due to the circumstance that import transactions are subject to greater control measures via the customs system.
• Information on weight and quantity may be subject to greater margins of uncertainty compared to information on value.

Intrastat covering trade with EU member countries is subject to considerably higher margins of uncertainty compared to Extrastat. Current data-editing measures give rise to corrections, but especially the lack of data reports constitutes a considerable source of uncertainty. Particularly in the first months, estimates for delayed data reports are replaced by actual data reports, which give rise to, e.g. changes in trade between different goods and countries. Estimating trade of the smallest business enterprises exempted from reporting data also contributes to the circumstance that the statistics at the most detailed level are subject to some degree of uncertainty.

The figures for total imports and exports from/to EU countries are considered to be of high quality in the final statistics as information is added with information from the VAT returns of the business enterprises, which cover all transactions of goods between Denmark and the EU countries.

At the detailed level, the reliability of the figures is affected by:

• No data reports from enterprises below the threshold limits of Intrastat.

• Imperfect and/or delayed data reports from enterprises obliged to report.

• Submission of inconsistent information, e.g. where the relationship between value and net weight in kg and/or supplementary unit seems unlikely.

• For reasons of resources, it is not possible to examine all data reports where (probably) inconsistent information has been submitted.

At the moment, there are no exact figures for the statistical uncertainty.

Sampling error

For non-EU trade, Extrastat, there is full coverage of population and sampling error is thus 0. In EU trade, Intrastat, the population is in principle a cut-off sample. The sampling error is not known.

Non-sampling error

The overall accuracy of Intrastat is affected by sampling error and non-sampling error combined. Non-sampling errors include measurement error and non-response error, i.e. missing or wrongful reports from enterprises obliged for Intrastat reporting or wrongful estimation of missing trade from enterprises which are exempted from reporting to Intrastat.

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 accurary levels of the two main sources for the statistics differ.

Extrastat covering trade with non-EU countries is generally of a high quality. However, the reliability of the figures at the detailed level is affected by:

• The figures on imports probably have a slightly higher quality compared to the figures on exports, due to the circumstance that import transactions are subject to greater control measures via the customs system.

• Information on weight and quantity may be subject to greater margins of uncertainty compared to information on value.

Intrastat covering trade with EU member countries is subject to considerably higher margins of uncertainty compared to Extrastat. Current data-editing measures give rise to corrections, but especially the lack of data reports constitutes a considerable source of uncertainty. Particularly in the first months, estimates for delayed data reports are replaced by actual data reports, which give rise to, e.g. changes in trade between different goods and countries. Estimating trade of the smallest business enterprises exempted from reporting data also contributes to the circumstance that the statistics at the most detailed level are subject to some degree of uncertainty.

The figures for total imports and exports from/to EU countries are considered to be of high quality in the final statistics as information is added with information from the VAT returns of the business enterprises, which cover all transactions of goods between Denmark and the EU countries.

At the detailed level, the reliability of the figures is affected by:

• No data reports from enterprises below the threshold limits of Intrastat.

• Imperfect and/or delayed data reports from enterprises obliged to report.

• Submission of inconsistent information, e.g. where the relationship between value and net weight in kg and/or supplementary unit seems unlikely.

• For reasons of resources, it is not possible to examine all data reports where (probably) inconsistent information has been submitted.

At the moment, there are no exact figures for the statistical uncertainty.

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

As the share of estimated figures is in the order of 20 to 30 pct. when the statistics are published for the first time, there are a number of deviations between the first and the final publication of external trade figures for a given month.

The inaccuracy with respect to the provisional statistics can be illustrated by the difference between the first provisional publication and the subsequent publications of statistics. Generally, there are greater differences between the figures for EU trade (Intrastat) between the first publication and the last publication of statistics than is the case for non-EU trade (Extrastat).