Accuracy and reliability

Overall accuracy

The register-based labour force statistic is the data foundation for the commuting statistic. I terms of sources of uncertainty it is especially the following that is relevant to the commuting statistic:

• Determination of the primary attachment to the labour market for a person with more than one job at the end of November: In these cases the primary job is determined by the number of hours worked. The job with the most hours is defined as the primary. For self-employed and assisting spouses the information about working hours is always imputed, and in some cases that goes for employees as well. For employees the imputed part has though decreased from 14 pct. in 2008 to barely 4 pct. in 2017. The imputation can in some cases mean that the wrong job is pointed out as the primary.

• Employed distributed by industry: There are some uncertainties concerning which workplace the specific employee job is situated, because some reports from the employers are insufficient. The insufficient reports causes a necessary search for and correction of errors regarding the workplaces, but even though the errors are corrected in the best possible way there will continuously be uncertainties about parts of the information about workplaces - especially on a detailed level. The uncertainties are especially linked to the detailed distributions of employment in the public sector and particularly on the municipality sector. In that area the distributions on industries within "residential care activities" (industry 87) and "social work activities without accommodation" (industry 88) are uncertain on a more detailed level, but also between the two industry. Detailed distributions on "Education" (industry 85) are also affected by uncertainties.

Sampling error

Not relevant for this statistic.

Non-sampling error

Nothing further to note.

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

RAS - the data foundation of the commuting statistic - is a total count and the data foundation is the Labour Market Account (LMA). In LMA various data sources are integrated, corrected and harmonized in one joined system. Since RAS is a total count of the population there is not the same uncertainties as with statistics based on surveys. Read more about the quality assessment of RAS in the documentation.

Concerning the calculated commuting distance it is also substantially to be aware that it reflects an ideal situation where every employed person is assumed to be travelling from residence to workplace at the shortest possible route and by car. The distance is therefore a measure of how far a person must travel to get to work, and not an expression for the real traffic pattern. Accessibility, preferences and other habits are not taken into account. Neither is public transportation which will often follow another route than the shortest. And finally is also happens that the workplace address refers to a head office while the real workplace is placed differently.

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

When the commuting statistic is published data is considered final. However data can be revised as a result of changes in methods or new information available. Since the data foundation for RAS changes to the labour market account (LMA) following changes have been made:

1. At the publication of figures for the end of November 2013, where the labour market accounts were used as the data basis for RAS for the first time, the data for 2008-2012 was revised.
2. At the publication in April 2016 the data was again revised back to 2008. This revision had only a very limited impact on the employed population and thus on commuting statistics.