, retail space, and industrial structures are classified as “ commercial real estate ", the classification of multi - family dwellings is not clear and depends on whether one follows the perspective of users or investors. data availability remains challenging, too. the number of transactions is lower than for residential real estate, and heterogeneity is more pronounced. in the absence of official data, analysts rely on private data provided by market observers. figure 5 depicts deviations in the measurement across indicators for price changes in german property markets. with regard to residential property prices in germany, analysts may consider four main indicators published by different data providers. in this case, they are confronted with measurement deviations of about 1 percentage point for the annual price change of the total market on average ( left - hand column ). for office and retail space, the mean absolute deviation is considerably larger at 2½ percentage points. this is one of the underlying challenges of assessing such data. 5 / 8 bis central bankers'speeches given that real estate prices have increased strongly, are risks to financial stability building up? two issues need to be considered. first, changes in prices need to be compared to changes in fundamentals such as income expectations, demographics, and the macroeconomic environment. these factors may indeed explain a significant share of the price increases in germany. but there is still an unexplained component, and that component seems to have increased over time. 3 second, risks to financial stability emerge if a strong rise in real estate prices coincides with a strong expansion in credit volumes and an easing of credit standards. the house price momentum has caused credit growth, too, to accelerate since the beginning of the upswing on the german property market. housing credit to households increased by 3. 7 per cent in 2016. this is lower than the long - run average : since the early 1980s, the growth rate of housing credit has been about 5 per cent annually. it is important to note that germany currently has no consistent reporting on credit standards, eg the loan - to - value ratio or the debt service - to - income ratio. the relevance of and urgent need for progress in the measurement of real estate prices is widely acknowledged. i am looking forward to the contributions that will be presented at this conference and encourage the statistical community to push ahead with this strand of research and practical implementation. 5. summing up to sum up, what can the conference contribute to these debates? let me return to the three questions raised at the beginning

expenditure weights from one base year to another, price and quantity effects often move in opposite directions. this suggests that substitution plays a significant role. in parallel to discussions about the boskin report, the ground was being prepared for the launch of the euro in europe. a number of key questions needed to be answered : why did eurostat conceptualise the hicp as a cost - of - goods index? why does the eurosystem define price stability as an increase in this index of below, but close to, 2 per cent over the medium term? papers presented at the 1999 meeting of the ottawa group provided answers. the eurosystem ’ s definition of price stability includes a safety margin against deflation. 1 / 8 bis central bankers'speeches within any country and, in particular, across the different economies within a monetary union, there is a need for structural change and adjustment of relative prices. in the presence of nominal rigidities, positive inflation allows for the required adjustment of relative prices. figure 1 shows that inflation differences in the euro area have been quite significant in the past 20 years, demonstrating the need for the adjustment of relative prices. price indices should be transparent and easy to communicate. the euro area ’ s hicp is a pure price index based on the laspeyres formula, which has advantages over a cost - ofliving index. a cost - of - living index requires the definition of consumer baskets with the same standard of living in the context of changing relative prices. this requires a utility framework. but how to define and measure individual preferences? how to aggregate across individuals? these questions are difficult to answer. such problems can be avoided with a pure price index. apart from substitution effects, shifts in expenditure weights are explained by other factors such as income effects. against this backdrop, hicp weights are updated more frequently in order to accommodate these changes. in april 2014, the ecb concluded in a monthly bulletin box that, “ [ o ] n the basis of the available evidence, it is not possible to estimate measurement bias in the euro area hicp ". in short, much remains to be done for researchers and statisticians to reexamine this important topic in price statistics. 3. the impact of digitalisation on price statistics digitalisation obviously has an important impact on price statistics. consumer behaviour and channels of distribution have changed profoundly, and weighting schemes need to take these changes into account. do updates of consumer baskets sufficiently account for the introduction of new ict goods?