Dokumentation og international benchmarking af bygge - Danmarks ...

Non-response errorsThe resulting variations in the index estimates are called non-responseerrors.The response rate in Norway is relatively high, almost 75 percent.The standard deviation due to non-response is normally calculated at between0.5 and 0.7 percentage points.Despite the obligation to respond, the nonresponse in Sweden in 2006was 17 percent on multi-dwelling buildings and 27 percent on collectivelybuilt one- or two-dwelling buildings.Summing upDataCalculating hedonic indices require reporting on both the actual pricepaid for the project and the characteristics of the building in question. Tobe able to perform the regression analysis the amount of data needed isalso relatively large.In times when the volume is going down in the construction industry, itcan prove difficult to compile true and fair indices.There is also the issue about timing that Sweden has chosen to solve bycollecting the price at the time of entering the contract instead of the actualprice paid at the end of the construction period. The alternative beingto have indices produced that relate to periods some time ago, when whatyou wanted was in fact short-term indicators.Calculation methodThe method as applied in Norway has been able to explain only about 30pct. of price variation as coming from the explanatory variables in the regressionfunction. In Sweden, the r-square has varied between 0,20 and0,73, which shows some variance in the models ability to explain pricemovements.The method requires that the regression model is kept updated at anytime. This is time consuming and requires an experienced staff. Boththings are easier to provide in a relatively large statistical bureau.97