Statistical processing

Source data

The rent survey is based on a sample of privately owned rented dwellings, social rental housing and cooperative dwellings. The rent development for the social rental housing is based on administrative data from The National Building Fund (Landsbyggefonden) and thus covers the entire population of social rental housing. Privately owned rented dwellings are covered by a sample of approx. 110.000 dwellings out of a population of approx. 500.000 privately owned rented dwellings. Cooperative dwellings are covered by a sample of approx. 600 dwellings. The same rental dwellings are included in the sample over time (a panel) as far as possible, but the sample is updated on a continues basis with newly built rental dwellings to ensure that the sample continues to reflect the population.

Frequency of data collection

Quarterly. Cooperative housing does only have a yearly collection.

Data collection

Data collection for the cooperative dwellings is based on yearly questionnaires and the questionnaires are sent to the owners or administrators of the dwellings. The information asked for is:

• The monthly rent, excluding heating and other special services (for example, garage space)
• In cases of rent changes as a result of improvement of the dwelling, the respondent is asked to inform the nature of the improvement and the share of the rent change that is caused by the improvement

The administrative data for social rental housing is received from The National Building Fund (Landsbyggefonden) while rents for the privately owned rented dwellings is received from The Danish Property Federation (trade association of the Danish property industry - EjendomDanmark).

Data validation

The data material received is examined for errors, both automatically and manually. In the automatic process observations are being flagged for further inspection if the price change compared with last perioed is more than plus or minus 10 percent. The observations are checked by contacting the data respondents. In the administrative data for social rental housing, non-plausible observations are removed mechanically when they fall outside pre-determined criteria. For the data for the private market data are treated the same way and we have a cooperation with The Danish Property Federation where we can ask for changes within our predetermined criteria.

Data compilation

The average rent development is calculated by dividing the rental housing by strata for resp. municipalities and type (private, public rental housing or cooperative dwellings); a total of almost 300 strata. Within each stratum, rent development is calculated by dividing an unweighted average by the current rent of the rental dwellings with an unweighted average of the rent of the rental dwellings in the previous period. Only rental homes where a rent has been registered in both periods are included. On the basis of the indices on municipality and type the indices on the different groupings is calculated, where the rent development in the 300 strata are weighted together with weights. The weights are based on estimated total rental sums in the population of rental housing within each stratum.

Adjustment

In calculating a price index it is assumed that the baskets of goods that are compared are identical, also with respect to the quality of the goods. Consequently, in the case of changes in quality the prices should, in principle, be adjusted for this. In the development of rents statistic quality improvements in the cooperative dwellings in the sample are handled by using values reported by the respondents for a given improvement and multiplying this value with a fixed percentage rate depending on the type of improvement. The improvements can be, for example, the addition of a balcony. The new calculated value is subtracted out of the rent increase before the total average rent increase is calculated. For the public rental housing based on administrative data and for the privately owned rented dwellings, it is not possible to directly correct for improvements in the rental housing.