Statistical processing

Source data

The primary source of the statistics is the Civil Registration System (CPR). The continuous updating of the Civil Registration System is thus the basis of the population statistics. The updating takes place in the individual municipalities as the municipal population changes because of births and deaths, migrations in and out of the municipality and changes in marital status for the citizens of the municipality. The Civil Registration System is a central system with a common database where all registrations are updated. The state makes the system available to the individual municipalities. The Danish Health Data Authority’s Birth Register and Cause of Death Register are the secondary sources providing data on births and deaths respectively.

Frequency of data collection

Data is collected on a daily basis from the Civil Registration System (CPR), while data is received from the Health Data Authority once a year.

Data collection

System-to-system delivery from the Civil Registration System (CPR) as Statistics Denmark daily receives a data delivery from CPR containing the births, deaths, migrations etc. reported the previous day to the municipal registration office. Data from the Danish Health Data Authority’s Birth Register and Death Register is received on a yearly basis and, subsequently, selected variables are used for the individual population statistics.

Data validation

The current updating of the Civil Registration System takes place in the municipalities. The civil registration number and the updating of residence information and marital status information etc. is required for a vast number of public services, which serves as continuous validation of the content of the register. This also lies at the root of Statistics Denmark’s decision to use the civil registration data for production of the current statistics. Statistics Denmark is in dialogue with relevant authorities to ensure that the updating is correct at the municipal level e.g. regarding the registration of migrations. The municipalities are responsible for registering residential addresses in the Civil Registration System. If a municipality suspect that a registered residence in the Civil Registration System (CPR) is incorrect, the municipality must look into the matter to ensure correct registration in CPR, cf. section 10(1) of the Executive Order on the Civil Registration System Act. CPR has a number of incorporated consistency checks to ensure against registration of invalid values. Cancellations/corrections in CPR, which are registered by the municipalities, are updated in Statistics Denmark’s database as they arrive. The published population figures therefore show the population with as current and correct data as possible at the time of publication. Statistics Denmark also performs a number of automatic checks to ensure the quality of the register and further checks in connection with the publication of the statistics. If relevant, inquiries from users may also give rise to checks.

Data compilation

The daily data deliveries from CPR contain the births, deaths, changes of address, migrations etc. reported the previous day to the registration offices (CPR) of the municipalities. For each person in CPR for whom an event is updated, Statistics Denmark receives the relevant information and then updates Statistics Denmark’s population database, which holds the previous information on residence, marital status, family, name, citizenship, national church membership status etc. A population statistical recording is created at the end of the quarter by extraction and delimitation of the population based on these basic tables. Migrations in and out are recorded according to when the migration was registered in Statistics Denmark’s population statistical registers. This means that all migrations are included in the statistics regardless if the migration has happened earlier than the year/quarter of the statistical recording.

Information on the persons’ mothers and fathers and their citizenship and place of birth is used to establish ancestry and thus the number of immigrants, descendants and persons of Danish origin in the population of Denmark. It is possible for persons to change between some of these groups, e.g. an immigrant may become a descendant if the parents were born in Denmark and at some point pass from foreign to Danish citizenship. A country of origin is allocated to both immigrants and descendants based on the information on either the person’s own or the parents’ country of birth and citizenship. If both parents are known, the country of origin is defined by the mother’s country of birth or citizenship respectively. If only one parent is known, the country of origin is defined by that parent’s country of birth. If this is Denmark, the country of citizenship is used. If none of the parents is known, the country of origin is defined by the person’s own information. If none of the parents is known, the country of origin is defined by the person’s own information as it is assumed that the country of origin for an immigrant equals the country of birth, whereas the country of origin for a descendant equals the country of citizenship. See the definitions etc. on the subject page on immigrants and their descendants. In case of dual citizenship (Danish and foreign), the Danish citizenship is applied as country of citizenship in the population statistics. The information on births from CPR are linked with information on births from the Danish Health Data Authority in order to assess single and multiple births as well as the child’s length and weight at birth. The number of births is used to calculate fertility rates and total fertility. The age-specific fertility is calculated as the number of liveborn children per year delivered by mothers in a given age bracket and the number of women in the relevant age bracket measured in thousands on 1 July of the year. The fertility rates are then used to calculate total fertility by adding the age-specific fertility rates. The calculation method was changed from January 2014, cf. method note on the subject page on fertility. The annual publication Befolkningens udvikling, which is published in Danish with a summary in English, also has age-specific fertility rates for men.

Furthermore, the publication contains calculated gross and net reproduction figures. The calculation of the gross reproduction figure is made in the same way as the calculation of total fertility, except that it only includes born girls. The net reproduction figure is found by reducing the number of women in the calculation by the mortality of the individual age brackets.

Information about deaths is linked with information on the cause of death from the cause of death register, so the deaths can be categorised by cause of death, sex, age and municipality. The figures for deaths are used to calculate life expectancy at both national level and municipal level. Life expectancy is calculated by first assessing the probability of dying at all age levels over a two-year period. The calculated death rates are then included as the basic information in the mortality tables used to calculate life expectancy. The mortality tables are based on a fictitious initial population of 100,000 people, and based on the age-specific death rates, it is calculated how many from the initial population are survivors at each age level from 0 to 110 years. This allows calculations of life expectancy, which is the expected average duration of life at a given age level. Read more in Method note on calculation of life expectancy. Based on the information about address in CPR, data is compiled on households, which consist of the person or persons living at the same address. The household can consist of one or several families. A family is one or more people living at the same address and having mutual relations. The relation may be e.g. marriage or registered partnership and parents/children, all of which appear as relations in the Civil Registration System. To be able to assess other couple families (cohabitation), it is assumed that two adults living together with a joint child are a couple, and they are called a Couple living in consensual union. If a couple has lived with a joint child on 1 January 1990 or on 1 January of a subsequent year, this is also defined as a couple living in consensual union. However, if joint children no longer live in the household, the parents must have lived together on 1 January all of the subsequent years. Two adults who live together, but do not have joint children, are also assumed to be a couple if their age difference is less than 15 years, they are of opposite sex, and family references in CPR do not indicate that they are related to each other, and there are no other adults on the address. Persons down to 16 years can be cohabiting. The adults may have separate children. In addition to the adult(s), both couple families and singles may include one or several children living at home. Children are here defined as persons who are under 25 years, unmarried, do not have children of their own and are not part of a cohabiting couple. If a child has a parent reference to at least one adult in the household, the child lives at home and is included in the family of the adult(s), otherwise the child is not living at home and constitutes his/her own family. The assessment of families and households is used to assess the number of children in different types of households and families. Children who do not live with both of their parents have a residence family (where the child has his or her address) and a parenting time family (where the child does not have his or her address). Based on the registers, the number of children living in different types of families, including sibling relations, is counted. The definition of children varies from one table to the next. In the tables fam133N and fam111N, children in the family are defined as described above: children who have their home at the same address as at least one of the parents, are under the age of 25 years, have never been married or in a registered partnership and do not have a child/children of their own who are registered in the civil registration system. In the same tables, children not living at home constitute families of their own. To be considered as children not living at home, they must not live with either of the parents, be under 18 years, never have been married or in a registered partnership, not have children of their own who are registered in the civil registration system, and not be part of a cohabiting couple. In the tables fam44N and fam44BA, families with children are defined as families with children under 25 years living at home. In the tables brn9-brn16, families with children are delimited only on the basis of the age of the children, i.e. persons aged 0-17 years. However, brn12 includes only families with children where the child lives at home in either the residence family or the parenting time family. In the civil registration system (CPR), information is registered for the individual person about marriages, which is used to calculate the average age of persons getting married for the first time as well as of all persons getting married. Moreover, the information on the two people of a marriage is combined, so that the number of marriages can be assessed, since only marriages are included where at least one of the spouses resides in Denmark at the time the marriage is contracted. If the other party has not resided in Denmark, it is not possible to determine the sex of that person. In these cases, the marriage will be defined as a marriage of an opposite-sex couple.

In addition, data on divorces is registered for the individual person residing in Denmark at the time of divorce. The information is linked together to assess the number of divorces. For divorces where one of the parties has not resided in Denmark, it is not possible to determine the sex of that person. In these cases, the divorce will be defined as a divorce of an opposite-sex couple. Divorce data is used to calculate the divorce rate, which is done in more or less the same way as the calculation of life expectancy for 0-year-olds. Thus, the current probabilities of divorce are calculated for all years of marriages up to 50 years. The calculation is based on the number of divorces in a calendar year relative to the number of remaining marriages on 1 July of the year following all lengths of marriage. In this way, the probability of divorce is calculated by the duration of the marriage. The probabilities of divorce for marriages that have lasted one year, two years, three years etc. up to 50 years put together result in the overall divorce rate. For more details, read the Documentation of divorce rate.

A person may get divorced or married several times in a year, and may thus be included in divorces and marriages several times. The number of changes of residence in Denmark within municipalities, between municipalities and between regions is assessed based on changes of address. A person may be included several times if the person changes his or her address several times in a year. Information about changes of address is combined with information from the Census of Housing in order to assess vacated abandoned dwellings by various characteristics, and information on type of family both before and after the move is used to assess various types of change of address. In addition, migrations in and out of the country are counted (immigration and emigration). A person may be included several times if the person changes his or her address several times in a year. E.g., a person may immigrate in February, emigrate in June and re-immigrate in November. In that case, the migrations of that person will be counted as two immigrations and one emigration. Asylum seekers who are granted a residence permit are counted as immigrants when they obtain their residence permit and are registered in the civil registration system.

Adjustment

No corrections of data are made in addition to those already described under data validation and data processing.