SSB uses data from the tax return for individuals and concluded that it was 257 853 secondary homes in Norway in 2021 (Abrahamsen, 2021). Ambita uses data from the Cadastre and the Register of Deeds (Grunnboken) and concluded that it was 392 754 secondary homes in Norway in 2021 (NEF, u.å.). It is a big difference, and it is interesting to find the main reasons why the discrepancies are so large.

The main goal in this report is to find the difference between the secondary housing statistics of SSB and Ambita. We tried to reproduce Ambitas data for 4th quarter of 2021 to compare with SSBs secondary housing population. We are using data from 4th quarter of 2021 because it is for the tax year 2021 SSBs last published figures on secondary housing. To reproduce Ambitas figures we used Ambitas “about the statistics” and additional information we received by email. We received a simplified description of how Ambita compiled their secondary housing population. This means that we had to make some assumptions, and we were not able to imitate Ambitas’ secondary housing population correctly. We still think that we have a good enough basis to make a comparison of main differences between Ambitas and SSBs secondary housing population, even though there may be a few points that we are missing by not having Ambitas’ actual population.

In the summary, the two most important reasons for the disparities between the secondary housing population will be presented.

Secondary housing is defined differently both in terms of definition and structure of the underlying data. SSB (which uses data from the tax returns) usually looks at the property level to define secondary homes, while Ambita looks at the utility unit level. In the tax returns the primary/secondary home variable is set at the taxable object level. The taxable object is usually at property level, but in some cases, this is deviated from, e.g. when a property is split because the entire property is not used for the same purpose (e.g. housing and business on the same property). A taxable object can contain up to several utility units. In many cases we are at different unit levels. When we compared the properties that were both In Ambitas and SSBs population we found 210 005 unique properties. 194 098 of the properties have the same number of dwellings as taxable objects. Of the remaining 15 907 properties, there are more dwellings than taxable objects on 15 518 of the properties. On these properties, there were a total of 36 059 dwellings in Ambitas data compared to 15 650 taxable units in SSBs data. That’s 20 406 more dwellings. This explains why SSBs data usually are at property level compared to Ambita at utility unit level.

The other biggest difference is that SSB are limited to two certain property types. Primary/secondary variable are only set on property type “share in housing cooperatives” and “housing including owner section” in the tax authorities property register (SERG). Ambita does not have a similar limitation and there is no corresponding property type in the Cadastre. A very large portion of the properties that are only in Ambitas data are located on properties that are defined as a farm property and holiday home property in SERG. There is a tax explanation for both. Farm properties have different taxable value calculations than “normal” dwellings. There are special rules in which you can categorize dwellings as a holiday home if certain conditions and documentation are met.