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Accuracy and reliability

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National Accounts, Economic Statistics
Sara Svantesson
+45 39 17 30 66

srs@dst.dk

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Waste Accounts

The quality is good concerning the figures for total amounts of waste as well as the amounts for different forms of treatment. The distribution of waste according to categories also has a good quality, even if it is most reliable at the aggregated level. At more detailed level, the precision is less due to measurement errors (in the reporting).

The detailed distribution according to industry groups is less precise. This stems from errors in the source data (measurement errors from the reporting) as well as from the assumptions made in the distribution of waste to detailed industry groups.

Overall accuracy

No quantitative assessment of total precision has been made.

Precision is high for the figures for total amounts of waste as well as the amounts for different forms of treatment. This evaluation is based, among other things, on comparisons to data from other source, e.g. on incinerated amounts of waste. The distribution of waste according to categories also has a good quality, even if it is most reliable at the aggregated level. At more detailed level, the precision is less due to measurement errors (in the reporting).

The detailed distribution according to industry groups is less precise. This stems from errors in the source data (measurement errors from the reporting) as well as from the assumptions made in the distribution of waste to detailed industry groups. Especially for the specific industry groups where 'hours worked' is used to distribute waste (as described under data compilation), the figures must be regarded as estimates only.

When using the statistic to calculate recycling percentages, it is important to note that the type of collection of waste influences the classification. E.g. a piece of plastic packaging will only be classified as plastic packaging waste if it is separately collected. If, on the other hand, it is collected unsorted, as part of mixed municipal waste, it will be classified as mixed municipal waste. Some of the waste flows (mixed municipal waste, waste suited for incineration) have the character of unsorted/mixed waste, whereas other waste flows only contain separately collected waste (plastics, cardboard, glass etc.). The waste accounts do not contain information on the amount of total waste from particular materials (e.g. plastic), only regarding the waste that has been separately collected. As a result, the statistic cannot be used for calculating the share of particular materials, e.g. plastic, waste collected for recycling. However, is it possible to see developments in the overall amount collected for recycling.

Sampling error

Not relevant for these statistics.

Non-sampling error

The main sources of non-sampling error are measurement errors and partial non-response in the source data (the electronically reported waste data received from the Danish Environmental Protection Agency) as well as the assumptions made in the complete and detailed distribution to industry groups. The Danish Environmental Protection Agency is working to improve the user friendliness of the waste reporting system to ensure better quality of reports.

The most significant effect on published figures is that waste from the transport industry is overestimated, due to reports from companies transporting waste being misreported as the generators of the waste.

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 quality is good concerning the figures for total amounts of waste as well as the amounts for different forms of treatment. This evaluation is based, among other things, on comparisons to data from other source, e.g. on incinerated amounts of waste. The distribution of waste according to categories also has a good quality, even if it is most reliable at the aggregated level. At more detailed level, the precision is less due to measurement errors (in the reporting).

The detailed distribution according to industry groups is less precise. This stems from errors in the source data (measurement errors from the reporting) as well as from the assumptions made in the distribution of waste to detailed industry groups. Especially for the specific industry groups where 'hours worked' is used to distribute waste (as described under data treatment), the figures must be regarded as estimates only.

There is an overestimation of waste generated by the transport industry, due to incorrect reports from enterprises transporting waste.

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 accounts are based on data from a system in the Environmental Agency. It is expected that data, also for previous years, will be revised as incorrect reports are identified and corrected. These revisions in the source data will be fully implemented in future publications of the waste accounts.