The statistic is based on a sample and the results are uncertain. The precision rely on the covering of the sample. Therefore the sample rate is bigger for vessels with high revenue. The aim is each year to include the 100 biggest vessels in the sample, and that 80 per cent of the total value of landings in Danish fishery come from the vessels in the sample.
Investments have the most uncertainty, because exchange of a vessel could result in closure of the fishing firm, and set up a new firm to run the new vessel.
In general terms the overall quality of the statistic should be evaluated as good. About half of the units in the population are included in the sample, but because the sampling is biased towards the biggest units, more than 80 per cent of the total revenue in Danish fishery is produced by the units in the sample (for 2018 nearly 87 per cent). Data for the remaining 13-20 per cent of the production/revenue is known from the register. Therefore it is only necessary to estimate the cost variables for less than 20 per cent of the total production.
Investment is the most uncertain variable, because replacement of a vessel may lead to closing down of the fishing firm, and the new vessel could then be run by a new fishing firm.
The main variables production and Gross output comes from administrative registers. There is no sampling error.
Estimated data for units not in the sample are calculated by simulating individual accounts. The simulated accounts can not be verified for errors, but the potential errors are relative to the coverage rate for the different statistical groups. For vessels above 24 meter the coverage rate is close to 100 per cent, while from 56 to 87 per cent of the revenue is covered for vessels between 15 and 24 meter. For groups of vessels less than 15 meter between 42 and 64 per cent of the revenue is covered, except mussel-dredgers and multipurpose vessels between 12 and 15 meter for which 32 and 25 per cent of the revenue is covered by the sampled units.
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.
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.
The quality of the collected data should be evaluated as good. The accounting forms are completed by professional accountants, who themselves have interest in the publication of the statistics, and who furthermore get paid for reporting the data. The harmonized accounting form, the tests and thorough examination of the reported accounts, and finally the comparison with register data all together contribute to secure the data quality.
Production and revenue from sales are important variables in the statistics that are registered for all units in the population. Therefore the coverage of the sampled accounts is known. In 2018 the sample covered 87 per cent of the revenue, therefore it was only necessary to estimate the cost for the remaining 13 per cent of the total revenue. The quality of the simulated accounts cannot be calculated (see model assumption error), but the good coverage of the reported accounts indicate, that the error on the estimated variables in the simulated units are less significant in the statistics.
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.
Originally only final figures have been calculated. But for 2012 and 2013 a two steps model has been used. By which the statistics first were calculated based on the sampled accounts, where the figures in the balance was preliminary, and later the value of immaterial assets was calculated based on registered quota transactions.