Residential property price index
This index is calculated on the basis of the euro price per square meter for new and used condominiums and for single-family houses. In the third quarter of 2017 some methodological changes were implemented.
Up to and including the second quarter of 2017, the dummy index was calculated by TU Wien (Vienna University of Technology) on the basis of data provided by EDI-Real GmbH. The calculation used a hedonic regression model with a fixed structure over time. This approach may produce biased estimates if the effects of the variables change over time.
The RPPI for Austria excluding Vienna was composed of the index for condominiums and the index for single-family houses at a ratio of 70% to 30%, with the aggregated index for condominiums comprising the index for new condominiums and that for used condominiums at a ratio of 12.7% to 87.3%.
All weightings were adjusted at three-year intervals. The weightings of the indices for new and used condominiums corresponded to the respective shares of new and used condominiums in the total number of residential property offers in the data pool. The aggregated index for condominiums (old and new) and the index for single-family houses, by contrast, were weighted according to the respective shares of sales of condominiums and single-family houses in the total number of sales transactions recorded in the Austrian land register for the period from 2008 to 2013.
With effect from the third quarter of 2017, some methodological changes were implemented. Now, the method of double imputation is applied as recommended in the Handbook on Residential Property Prices Indices by Eurostat. Instead of linear dummy hedonic models, generalized additive models (GAM) are calculated. Rather than on the database provided by EDI-Real GmbH, the index is now based on a more comprehensive database provided by the Internet platform JUSTIMMO operated by B&G Consulting & Commerce GmbH.
Indices are calculated for new and used condominiums, as well as for single-family houses. Weighting is no longer necessary, as the models are based directly on the geographical area for which the index is calculated. The data series up to the second quarter of 2017 and those from the third quarter of 2017 are linked together. For more details about the applied methods see Brunauer et al. (2017) Der österreichische Wohnimmobilienpreisindex: Methodische Verfeinerung 2017 in the OeNB publication Statistiken – Daten und Analyse Q4/17 (available in German only).
OeNB, DataScience Service GmbH (DSS), Vienna University of Technology, Prof. Feilmayr.