Accuracy and reliability

Overall accuracy

The general quality and reliability of the Civil Registration System (CPR) is regarded as very high, since correct registrations in CPR is required to be able to lead a normal life in Denmark with access to a general practitioner, a NemKonto bank account, employment in a business, starting your own business, participating in elections etc. Moreover, the municipalities are required by the Civil Registration System Act to ensure correct registration in the system of all citizens in the municipality. A few issues remain, however: These are especially associated with the registration of emigration from Denmark. In this connection, foreign students in particular pose a challenge, as they do not always remember to de-register from CPR when they leave Denmark. Delays in the registration of immigrations and emigrations also affect the assessment of the population. It is estimated that the population figure at the end of the year is overestimated by 11,500 emigrants who have failed to report their emigration and underestimated by 1,500 immigrants who have failed to report their immigration. Overall, this means that the population figure is overestimated by 10,000 or 0.14 per cent. An assessment shows that in the beginning of 2008, approximately 18,000 people were registered in CPR who had no contact with authorities from 2008 to 2010 besides receiving their pension. The group also includes e.g. people on round-the-world trips or pensioners staying abroad who should have reported emigration and who later move back to Denmark. However, the group also includes permanently emigrated people cf. the above and people who are later registered as dead.

Moreover, there is some variation as to when citizens from various countries are registered with a residential address when they immigrate into Denmark. Persons who move to Denmark from another Nordic country or who are citizens of an EU/EEA country or Switzerland are entitled to stay in Denmark for up to six months without being registered with a residential address in the Civil Registration System. They are not required to register until they decide that their stay will last for more than six months. Everyone else is required to register with a residential address when staying for more than three months. When emigrating, persons who intend to move abroad for at least six months must report this to the Danish National Register, so that they will be deregistered. Specifically for persons emigrating to Sweden and Finland, the stay must last for more than 12 months. Only deregistered persons are included in the figure for emigration.

In the assessment of the number of cohabiting couples, it is assumed that two people are a couple if they are of opposite sex, live together and their age difference is less than 15 years. It has not been examined how many of these cohabiting couples are in fact couples, but it is likely that some of them will simply be e.g. two students of opposite sex who share a flat. Accordingly, the number of cohabiting couples of opposite sex may be overestimated, although there may also be couples who are not included due to an age difference of more than 15 years.

It is not possible to include two people of the same sex as a cohabiting couple (due to the definition). This means that the number of same-sex couples is underestimated.

The number of same-sex marriages/divorces may be underestimated, while the number of opposite-sex marriages/divorces may be overestimated. This applies only for marriages and divorces where one of the parties has not resided in Denmark.

Sampling error

Not relevant for these statistics.

Non-sampling error

Corrections and cancellations of registrations in CPR are made on an ongoing basis. The vast majority of corrections and cancellations are made immediately after an error is observed in CPR, and thus do not pose a problem for the statistics, which are not published until 30 days after the cut-off date. The statistics are based on the registration date in Statistics Denmark’s population register for immigration and emigration respectively rather than the date of the event. Especially in connection with emigrations, there may be relatively long delays in the registrations in CPR. This means that the migrations of individuals may be included in the statistics a year later than the migration actually took place. In 2020, as much as 98 per cent of the immigrations were reported soon enough to CPR to be included in the data for the right year, while this was the case for 79 per cent of the emigrations, cf. www.statistikbanken.dk/bev107. In recent years, this percentage has remained at the status quo for immigrations and been declining for emigrations. A cause of death is missing for approximately 1 per cent of the deaths, and references to parents are missing especially for people born before 1950. Life expectancy disaggregated at municipal level is intended for limited populations in the individual municipalities. This means that the death rates used to calculate life expectancy become more exposed to random variations. Especially small municipalities may see variations in life expectancy as the share of deaths in the municipal population can vary randomly from one year to the next.

Incorrect addresses, which affect the assessment of families and households in particular, involve certain challenges. People without a permanent residence are a source of uncertainty. They are registered under special municipal addresses of a fictitious nature and are managed by the local civil registers. These addresses are reserved for people who cannot be registered at a residence for some reason. E.g. homeless persons, sailors, posted diplomats and certain other posted persons. Read more about the quality of the municipalities’ address registration in a survey by VIVE (in Danish).

Another source of uncertainty regarding households is communal dwellings (e.g. nursing homes) where the residents are sometimes registered under individual addresses and sometimes with a common address. For marriages and divorces where one of the parties is unspecified because the person in question has not been registered as a resident in Denmark, it is not possible to determine the sex of that person, which gives cause for uncertainty as to the distribution of marriages/divorces and whether a same-sex couple or an opposite-sex couple is concerned.

In the assessment of the number of cohabiting couples, it is assumed that two people are a couple if they are of opposite sex, live together and their age difference is less than 15 years. It has not been examined how many of these cohabiting couples are in fact couples, but it is likely that some of them will simply be e.g. two students of opposite sex who share a flat. On the other hand, same-sex couples are not included (unless they have joint children and live in consensual union or they are married).

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 statistics are based on the population registered in the Civil Registration System (CPR). In general, the information in CPR is considered to be reliable and in most cases up-to-date; see e.g. a report from the Ministry of Economic Affairs and the Interior in 2017 on the data quality in CPR and a report from VIVE in 2020 on the quality of the registration of residence in CPR (both reports are in Danish). There is a challenge in using only CPR as a source, as people who move to Denmark intending to say in the country for less than three months are not registered in CPR until later if they decide that they want to stay in Denmark for a longer period. Similarly, some people fail to report that they are moving out of the country, e.g. foreign students. If you want information on these groups in particular, the accuracy is thus lower than for the total population figure. The information in the population statistics is limited to the information in CPR, which constitutes another challenge. This means that you cannot get direct information on e.g. sexual identity, and the assessment of families is subject to a number of assumptions with inherent uncertainty compared to an assessment based on information from the persons involved. An alternative source of statistics on the population is actual surveys, but for the total population figure, this would yield a more costly, time-consuming and probably more inaccurate result. Only few corrections appear for CPR later than the 30-day delay after the end of a quarter. We have chosen not to revise data back in time, since the changes are so negligible that for all practical purposes, they have no relevance.

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

It is possible to revise the figures for deaths that are published weekly. The annual statistics are not revised; however, the annual statistics are compiled with a wider time gap to the reference time than Q1, Q2 and Q3, so that registrations arriving late can also be included.