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Accuracy and reliability

Contact info

Department of Social Statistics, Population and education
Annika Klintefelt
+45 39 17 36 78

akf@dst.dk

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Census of Housing

The degree of uninformed information for each variable is very little. Close cooperation between the BBR-authority and the Population Register in each municipality ensures a good match between the addresses in the two registers.

All property owners are obliged by law to notify changes such as extensions, demolitions or a new roof to the municipal BBR-authority. It is up to the homeowners to update information in BBR themselves, so it is doubtful that changes, for example in the number of rooms, toilet / bathroom conditions or change of heating are always notified BBR.

Overall accuracy

The degree of unknown variables is very small. According to the rules and regulations laid down by the Ministry of Economics and Business Affairs, public authorities and owners of buildings and dwellings are asked to provide information for maintaining the register. Owners are obliged to ensure that real and actual figures are continuously supplied. The main source of uncertainty is that there are lacks in reporting. The deficiencies are caused by ignorance, neglect, forgetfulness or otherwise. For example, it is uncertain to what extent the citizen reports a change in the number of rooms when a remodeling or heat source is changed.

Quality and accuracy of information in the BBR:

Ownership: Before 2010 ownership information was not available for owner-occupied flats (se definition). In 2012 and 2013 there was a problem obtaining correct ownership on dwellings especially those owned by non-profit building societies and housing societies. This was caused by the Land Registration being digitized.

Use: The number of dwellings with the use as residential buildings for communities are not at all representative of the total number of dwellings for this purpose. These dwellings will most often be placed with use as terraced, linked or semi-detached houses or multi-dwelling houses.

The Central Register of Buildings and Dwellings was established in 1977 by compiling information collected from owners of real property. Figures on living space and time of construction for older buildings may be subject to errors. Especially in cases where the building has not later been involved in an administrative building or development case. This is, of course, due to the lack of accurate data by the owners as far back as 1977.

The accuracy of the Central Population Register is known to be very high. A close co-operation between the municipal authorities of the Central Register of Buildings and Dwellings and the Central Population Register ensures a high consistency between the addresses of the two registers.

The vast majority of CPR-addresses - 96.7 pct. (1. January 2020) are matched perfect to a BBR-address with only one unit associated.

  • 99.6 pct. of the CPR-addresses are matched completely to an address in BBR.
  • 0.1 pct. of the CPR-addresses are matched to an empty dwelling at the same floor or same staircase.
  • 0.02 pct. of the CPR-addresses are aggregated with one or more CPR-addresses at the same floor
  • 0.3 pct. of the CPR-addresses find no dwelling in the BBR. These includes households on secret addresses and other not physical addresses ie. homeless, few allotment houses, houseboats and possibly new not yet completed dwellings.
  • 0.5 pct. of the population do not find a dwelling in the BBR-register.

Match of addresses on floor or stairway-level are considered as giving a good result at the overall level, but are not necessarily correct at the record level.

The number of unoccupied dwellings is very dependant on correct registration of units being registered and especially deregistered, when they are no longer available as dwellings.

Sampling error

Not applicable

Non-sampling error

Only a very small share of the population cannot be placed in a dwelling. In 2019, there are 32.000 people who do not match. One reason seems to be that the addresses in the CPR are not always updated. Furthermore, only the BBR units that can be placed in a building are included. Military-owned buildings are discretionary in the BBR, so the associated units are not included in the dwelling statistics. For example, all units on Christiansø are discretionary. There are also households at secret addresses and other non-physical addresses (eg homeless), some garden association houses, houseboats and possibly. new housing that has not yet been completed.

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

No real measure of quality is performed on the information in the Census of Housing. The vast majority of population is placed in a dwelling and the information in the BBR are considered reasonable. Most homeowners are not aware of the obligation to update the information in the BBR.

Known errors in the Census of Housing are:

-Problems getting correct ownership codes for the dwellings, especially in 2012 and 2013. Especially the number of dwellings owned by Non-profit building societies is too low (3-4 pct. in 2012) -Most of the residential buildings for communities are no longer registered with use as residential buildings for communities at the dwellings level. Since 2000 most of the Municipalities has changed the registration of the use of these dwellings which means that by 2014 there has been a 70 pct. decline in the number of these dwellings.
- The Municipality of Frederiksberg has registered far to many dwellings owned by non-profit building societies (25-30 pct.) in 2010-2015 - The Municipality of Svendborg had in 2010 error in tenure on approx. 20.000 dwellings, ie. 75 pct. of their dwellings. This has implications for the country total. - Some unoccupied student hostel dwellings in Copenhagen have been unoccupied since 2010, which means that these units probably are not used for this purpose anymore. - Some vacation rentals are in the BBR registered with use as as proper dwelling, which means that they in the census are counted as unoccupied dwellings.

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 statistics are published.