Accuracy and reliability

Overall accuracy

Projections are inherently associated with uncertainty. The purpose of the projection is first and foremost to give an estimate of how the population will develop given a number of assumptions. Whether these assumptions are consistent with the actual development is subject to uncertainty. The further into the future you look, the higher the uncertainty.

In the country projection, it is especially the uncertainty regarding immigration of foreign citizens and the future development in fertility that are worth paying attention to. For the provincial and municipal projections, you should pay particular attention to the uncertainty regarding in-migration and out-migration. It is assumed in the projection that the current migration pattern based on historical data for the last four-year period will stay at the same level throughout the projection period.

The projections are deterministic, i.e. based on historic experiences – if the development that we have seen so far continues then the development in the years to come will be like this. The projection only contains one scenario for the future development. To a wide extent, the uncertainty at municipal level is linked to the fact that local development plans and local decisions altogether are not part of the model. Uncertainty is an important factor, however, the uncertainty is not calculated, nor is it possible to calculate it with the present projection models.

The number of children born in future depends on the development in fertility. The uncertainty in this variable is thus significant because of the uncertainty in the future fertility development. This affects e.g. the number of children in preschool class six years into the projection period.

The future number of deaths is subject to a certain amount of uncertainty due to the unpredictable development in mortality. For a long time, the development in mortality has been declining and for that reason, it may be regarded as simpler to model than fertility and migration. First and foremost, deviations in this component affect the elderly part of the population. Immigration is subject to a significant level of uncertainty due to the highly fluctuating movements and unpredictable development. This applies primarily to immigration of foreign citizens. The number of people immigrating is influenced by conditions in Denmark as well as conditions abroad. The Danish migration policy also has an impact on how many people are granted a residence permit in Denmark.

Emigration is subject to uncertainty due to the highly fluctuating movements in migrations and an unpredictable development. The uncertainty of emigration is also caused by uncertainty in relation to the future immigration. Many immigrants emigrate within a relatively short span of time from their immigration, and high immigration will thus result in high emigration. The uncertainty regarding migration between municipalities in Denmark is important. The number of people moving to or away from a municipality is affected by e.g. job opportunities, access to housing and financial situation.

If the projection for all of Denmark is inaccurate, this will affect the municipal projections so that they are also inaccurate. Especially in 2015, it turned out that the number of refugees and reunited families was underestimated.

Because the projection model uses a four-year average, the projection will not reflect a trend. If a municipality has a soaring or plummeting population, the model will even out this development. Since the projection is for 25 years ahead in time, it is reasonable to use a more cautious approach to population growth/population decline. The municipal projection is “mechanical” in the sense that it does not incorporate factors beyond the strictly demographic conditions. Thus, the demographic consequences of decisions e.g. to increase housing construction are not included.

Statistics Denmark’s population projection has a very important restriction in that the sum of populations projected for municipalities must equal the projected country population. It is not possible to add to the population in one municipality without subtracting a corresponding number from other municipalities. Consequently, it would be possible to make a more accurate projection for the individual municipality seen in isolation if it did not have to be balanced against the result of all other municipal projections.

Sampling error

Not relevant for these statistics.

Non-sampling error

The projection describes the future population, which is inherently subject to uncertainty.

If the actual development deviates from the model assumptions, which it is bound to do to some extent, the future population will not correspond to that of the projection.

Assumptions of the 2023 projection for the whole country:

Fertility

Future fertility levels are difficult to predict. No methods can remove the great uncertainty with respect to assumptions on fertility development. In the short term, fertility may show considerable variations. From 2010 to 2011, total fertility in Denmark thus dropped from 1.88 to 1.76.

Long-term levels of fertility:

· Women of Danish origin, Danish citizenship: 1.90 · Women of Danish origin, foreign citizenship: 1.90 · Immigrants, non-Western with Danish citizenship: 1.70 · Immigrants, non-Western with foreign citizenship: 1.96 · Immigrants, Western with Danish citizenship: 1.73 · Immigrants, Western with foreign citizenship: 1.76 · Descendants, non-Western with Danish citizenship: 1.90 · Descendants, non-Western with foreign citizenship: 1.90 · Descendants, Western with Danish citizenship: 1.75 · Descendants, Western with foreign citizenship: 1.75

In the projection of fertility, you maintain the current trend for the first projection year. Only then, fertility will gradually approach the long-term level.

Transition rates:

Newborn babies with a mother who is an immigrant or a descendant can be categorised either as descendants or as persons of Danish origin. The categorisation of the child depends on the ancestry and citizenship of both the mother and the father. In the projection, newborn babies are broken down by origin in accordance with the pattern applicable in the period 2019-2021. E.g., 18,4 per cent of newborn babies were categorised as of Danish origin when the mother was a non-Western immigrant with Danish citizenship. The shares are kept at the same level throughout the projection period.

The share of newborn babies that are categorised as of Danish origin, disaggregated by the mother’s origin and citizenship:

· Women of Danish origin, Danish citizenship: 100 per cent · Women of Danish origin, foreign citizenship: 100 per cent · Immigrants, non-Western with Danish citizenship: 18.4 per cent · Immigrants, non-Western without Danish citizenship: 16.6 per cent · Immigrants, Western with Danish citizenship: 41.3 per cent · Immigrants, Western without Danish citizenship: 18.9 per cent · Descendants, non-Western with Danish citizenship: 100 per cent · Descendants, non-Western without Danish citizenship: 30.9 per cent · Descendants, Western with Danish citizenship: 100 per cent · Descendants, Western without Danish citizenship: 23.0 per cent

Mortality

Age- and sex-disaggregated mortality rates are projected based on the development in the period 1990-2022 using a variant of the Lee-Carter method. Mortality is not disaggregated on different groups of ancestry, which is mostly due to a lack of data on immigrants and descendants. It is thus assumed that the age- and sex-disaggregated mortality rates are the same for persons of Danish origin and all groups of immigrants and descendants. The projection of mortality rates results in life expectancies for 0-year-olds in 2059 of 86.9 years for men and 89.3 years for women.

Immigration and emigration

Immigration to the population groups consisting of persons of Danish origin and descendants is determined based on estimated immigration rates and the size of the resident population in each projection year. The same applies to immigration to the groups of immigrants with Danish citizenship. Immigration propensity is calculated broken down by sex, age, citizenship, origin and - for the groups of immigrants - also basis of right of residence. Immigration propensity is assumed to be constant throughout the projection, which is why a change in the absolute extent of immigration will be reflected in the size of the resident population.

Contrary to the other population groups, immigration to the groups consisting of immigrants without Danish citizenship from Western and non-Western countries is assumed to be determined exogenously. This type of immigration is typically the most sensitive to changes in politics concerning immigration or international matters. Thus, this type of immigration shows the highest variations in the scope of immigration year on year and, consequently, it is challenging to estimate the level ahead. Including the basis of right of residence in the model is estimated to make it easier to determine the extent of gross immigration, as this is now based on the development in immigration for each basis of right of residence rather than on the basis of the total flow. The immigration figures calculated for the projection indicate persons who were not in the population at the beginning of the year and who subsequently immigrate and are in Denmark by the end of the year. This is why they are not directly comparable with the higher figures published in Statbank Denmark. The figures in Statbank Denmark also include persons who immigrate during the year and have emigrated before the end of the year.

Since many immigrants also emigrate each year, net immigration is significantly lower. For all ancestry groups, the annual emigration is based on calculated emigration rates for all groups of sex and age. Emigration rates are kept constant throughout the projection period.

Assumptions of the 2023 projection for provinces:

Fertility

Age-specific fertility rates are calculated at provincial level. For each province, the age-specific fertility rates for the four-year period 2019-2022 are used as a basis. The development in fertility that is assumed in the country projection rubs off on the regional fertility through a balancing procedure, which ensures that the sum of figures for provinces matches the country projection figures. The geographical fertility differences are maintained throughout the projection period. The fertility assumptions are further described in the declaration of contents for the population projection for all of Denmark.

Mortality

In the regional projections, the calculations are based on mortality rates disaggregated by sex and age for all provinces. They are calculated on the basis of the mortality 2018-2022, corresponding to the latest publication of figures concerning life expectancy. 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.

Out-migration

It is assumed that the moving pattern for the individual provinces throughout the projection period corresponds to the average of the sex-specific and age-specific out-migration rates in the period 2019-2022. In the provincial projections, no distinction is made between out-migration due to internal migration in Denmark and out-migration due to emigration. Out-migration is not calculated at regional level.

In-migration

The number of refugees in 2023 and 2024 is distributed based on municipal quotas for refugees.

Any other in-migration is calculated on the basis of the relevant province’s share of other in-migration in the period 2019-2022. In the provincial projections, no distinction is made between in-migration due to internal migration in Denmark and in-migration due to immigration. In-migration is not calculated at regional level.

Assumptions of the 2023 projection for municipalities:

Fertility

Fertility is based on age-specific fertility rates calculated separately for all of the 98 municipalities for the four-year period 2019-2022. The fertility development assumed in the projection for the whole country rubs off on the regional (provincial) fertility via a balancing procedure, which ensures coherence between the number of births in the provincial projection and 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.

Mortality

In the municipal projections, the calculations are based on mortality rates by sex and age for the province in which the municipality is located. They are calculated on the basis of the mortality rate 2018-2022, corresponding to the latest publication of figures concerning life expectancy. In the calculations, it is assumed that all municipalities within a province have the same mortality. Coherence is ensured between the number of deaths in the provinces and the number of deaths in the provincial projection using a balancing procedure, which at the same time applies the country projection’s development in mortality in all provinces, but maintains the regional differences in mortality rate.

Out-migration

For each municipality, sex-specific and age-specific out-migration rates are calculated on the basis of out-migration in 2019-2022. In the municipal projections, no distinction is made between out-migration due to internal migration in Denmark and out-migration due to emigration.

In-migration

The number of refugees in 2023 and 2024 is distributed based on municipal quotas for refugees.

Any other in-migration is calculated on the basis of the relevant municipality’s share of other in-migration in the period 2019-2022. In the municipal projections, no distinction is made between in-migration due to internal migration in Denmark and in-migration due to immigration.

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 purpose of the projection is primarily to give an estimate of how the population will develop given a number of assumptions. Whether these assumptions are consistent with the actual development is obviously subject to uncertainty. The further into the future you look, the higher the uncertainty.

In the country projection, it is especially uncertainty regarding immigration of foreign citizens and the future development in fertility that are worth paying attention to.

For the provincial and municipal projections, you should pay particular attention to uncertainty regarding in-migration and out-migration. It is assumed in the projection that the current migration pattern based on historical data for the last four-year period will remain at the same level throughout the projection period.

The projections are deterministic and, for that reason, they contain only one scenario for the future development. However, uncertainty is an important factor, but uncertainty is not calculated, nor is it possible to calculate using the present projection models.

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

Only final figures are published.