Statistical processing

Source data

The civil registration system (CPR) is the source of all basic data used in the projections.

Frequency of data collection

All data used in the projections is annual data.

Data collection

All population data originates from the civil registration system (CPR). Thus administrative data is applied.

Data validation

There is no troubleshooting of input data, since CPR validates data themselves. Cancellations/corrections from CPR are updated in Statistics Denmark’s database as they arrive.

Data compilation

In practice, a projection is first made for the whole of Denmark, then the provincial projection, which is balanced against the country projection. Subsequently, the municipal projection is made, where he municipalities’ provincial total is balanced against the results from the provincial projection.

Below you will find a description of how the key parameters used in the model are handled. The description regarding the country projection is reproduced from DREAM’s documentation.

Births

The number of births in a given year depends partly on the age-specific fertility and partly on the number of women of childbearing age. The age-specific fertility indicates how many children a woman of a given age has on average. By multiplying the age-specific fertility for all ages with the number of women of the given age, you get an estimate of the number of births.

The total number of newborn babies is broken down by sex, assuming that a constant share of all newborn babies are boys. The share of baby boys is calculated based on the historic data period that is available. Based on the mother’s group of origin, the origin of all newborn babies is determined using a probability distribution to end up in separate groups of origin. The probability distribution is constructed on the basis of historic experiences.

At the municipal and provincial level, age-specific fertility rates are calculated on the basis of the average for the last four years. The development in the municipalities’ fertility rate is balanced against the development for the province. In this way, differences between the municipalities are maintained. Municipalities have different baselines when it comes to fertility, but they develop by the same rate. This balancing procedure where a course for the fertility that is presupposed in the projection for the whole country rubs off on the regional (provincial) fertility via a balancing procedure. This ensures coherence between the number of births in the provincial projection and the number of births in the country projection.

Via a similar balancing procedure, agreement is ensured between the number of births in the provincial projection and the number of births in the municipal projection. This ensures that the sum of figures for provinces and municipalities corresponds to the numbers in the country projection. The geographical fertility differences are maintained throughout the projection period.

Immigration

Immigration to Denmark in a given year is divided into two types of immigration in the projection model. Population groups without Danish citizenship account for a given inflow of immigrants differentiated on the basis of right of residence, while population groups with Danish citizenship account for re-immigration, which is calculated on the basis of immigration rates. The re-immigration rate is assumed to be constant in the projection period.

In the projection at municipal level, no distinction is made between in-migration from abroad (i.e. immigration) and in-migration from other municipalities.

Deaths

The number of deaths in a given year depends partly on the age-specific mortality rate and partly on the number of persons at each age. The age-specific mortality rate indicates the probability of dying at a given age. By multiplying the age-specific mortality rate for all ages by the number of persons at each age, you get an estimate of the number of deaths.

A projection of the age-specific mortality rate is used as future mortalities. In this projection, it is assumed that the future development in a given age-specific mortality can be derived from the historic development in the age-specific mortalities.

In the regional projections, the calculations are based on mortality rates disaggregated by sex and age for all provinces. Mortality rates for the last four years are used in the calculations. The development in the country projection is applied to the provinces in connection with a balancing procedure, which ensures that the sum of deaths in the provinces matches the number of deaths in the country projection. The mortality differences between the provinces are thus maintained throughout the projection period.

Mortality rates are not calculated at municipal level. Mortality rates for each municipality are based on the last four years’ mortality rates for the province to which the municipality belongs. In practice, information is required for all ages from 0 to 110 years, and because of the stringent level of detail required, calculations are not made for the individual municipalities. It is thus assumed that mortality is the same for all municipalities in a given province. The development in mortality is given by the development in the projection for the whole country. Each province has a different baseline when it comes to mortality, but they develop by the same rate. Coherence is ensured between the number of deaths in the provinces and the number of deaths in the municipal projections through a balancing procedure.

Emigration

The number of people who emigrate from Denmark in a given year depends partly on the age-specific emigration rates, which also depend on origin and basis of right of residence, and partly on the number of persons at each age. The emigration rates are calculated based on historic data. By multiplying the age-specific emigration rate by the number of persons of a given age and given origin and basis of right of residence, you get an estimate of the number of people who emigrate from Denmark. The emigration rate is assumed to be constant throughout the projection period.

In the projection at municipal level, no distinction is made between out-migration to other countries (i.e. emigration) and out-migration to other municipalities.

In-migration and out-migration

In the municipal projection, no distinction is made between internal migration on the one hand and immigration and emigration on the other. Anyone taking up residence in a municipality is part of an in-migration, regardless whether he or she comes from abroad or from another municipality. The same applies to migration out of a municipality. This is out-migration, regardless whether people move abroad or to another municipality. This also applies to the provincial projection, where no distinction is made between migration due to movements between provinces in Denmark and migration as a result of immigration and emigration.

Data for the last four years is applied for migration. For each municipality, out-migration rates are calculated for all ages and both sexes. For each municipality, it is calculated for each age and sex how much of total in-migration to the province the municipality accounted for in the last four years. In-migration is calculated based on the relevant province/municipality’s share of total in-migration into provinces/municipalities in the country in the last four-year period.

Both out-migration rates and in-migration shares for the last four years are assumed to be constant throughout the projection period. It is presumed that the moving pattern for the individual provinces and the individual municipality throughout the projection period corresponds to the average of the sex-specific and age-specific out-migration rates in the last four-year period. Since 2016, a different method has been applied. For these years, Statistics Denmark has distributed the in-migration of refugees according to the distribution plan for refugees determined by the Danish Immigration Service.

Any other in-migration is distributed according to out-migration rates and in-migration shares for the last four years.

Change of citizenship

The number of people without Danish citizenship who change citizenship in a given year is determined based on the age-specific change of citizenship rate. This is multiplied at each age by the number of people without Danish citizenship, whereby you get an estimate of the number of persons who change citizenship. The change of citizenship rate is assumed to be constant in the projection period.

The first projection year is calculated for each sex and age group, balanced against the projection for the country or province, and the result then becomes the opening population the following year with the age plus one year.

In the calculation of the provincial projection, out-migration rate is first multiplied by mortality of the opening population. The relationship between the number of deaths in the country projection and the sum of the calculated number of deaths for all provinces is taken into consideration, so that the sum is balanced. The balanced number of deaths and the out-migration number are deducted from the opening population of the province, and the remaining population in all provinces is summed up. The difference between this figure and the country projection estimate for the closing population is multiplied by the share that the province has received on average of all in-migrants in all provinces in the last four years (for each sex, age).

The number of children born is calculated as the sum of all one-year fertility multiplied by the average number of women in the age group ((opening+closing year)/2). Boys account for 51.4 of these, girls account for the remaining. The number of children born is balanced against the country projection. Out-migration, deaths and in-migration of 0-year-olds is calculated as for the other age groups. The total closing population is calculated, and it then constitutes the opening population of the next projection year - only difference being that everybody is a year older. Input data for the regional model consists of:

1. Calculated fertility, mortality and in- and out-migration rates for all provinces and municipalities
2. Opening population in municipalities and provinces the first year
3. Data from the country projection and later the provincial projection is used to balance population, births and deaths of the separate projection years.

The first two products are based on Statistics Denmark’s population registers, which in turn reflect events registered in the civil registration system (CPR).

Fertility, mortality and migration rates are based on the average of the last four years’ data for provinces and municipalities respectively. Data is created for both sexes and age groups 0-109 years, however, fertility is only created for women aged 15-49. Mortality is only created at country level, whereas the other rates are created at both provincial and municipal level.

Fertility is calculated as the number of children born according to the mother’s age divided by the average of the opening and closing population’s number of women in the given one-year age group in the area. Since this fertility curve is not even in the majority of municipalities and provinces – despite a four-year average – the curve is smoothed using a transreg procedure.

The mortality rate is calculated as the number of deaths in the year divided by the opening population disaggregated by sex, age and province. Since the mortality for the oldest citizens is based on a few events, a smooth curve is made for people above the age of 90 based on the mortality curve for the 60-89-year-olds. Mortality at the provincial level is used in the provincial projection as well as in the projection for all municipalities in the province.

In addition, the opening population in provinces and municipalities at the beginning of the year and output data from the country and provincial projections, respectively, are loaded for balancing of each projected year.

Please refer to the extensive documentation of the projection, which is available at DREAM’s website. Documentation of the projection is also available on the subject page on Population and population projection.

Adjustment

Not relevant for these statistics.