1. Comparison through estimates – the example of the European Urban Audit Beijing Forum on Metropolitan Statistics 20-21 Oct.2008 Klaus Trutzel Bureau for Statistics and Urban Research of the City of Nuremberg (Germany) - German National Urban Audit Coordinator - 2006

2. Purpose of the Urban Audit is to provide comparable data for the analysis of the quality of life in now more than 350 European and Turkish cities. 1. Background The European Commission initiated, at the end of the 1980s, the Urban Audit as a basis for their regional and urban policy. This project is soon beginning its 4th round of data collection. Eurostat, the Statistical Office of the European Union, has made great efforts to show the National Urban Audit Coordinators ways to provide complete and comparable data by requesting estimations wherever possible. 2 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008 27 countries are now contributing to this project. With their different social, economic and administrative background the countries differ in -data availability -data sources -data definitions -delimitation of urban areas

3. Source: Eurostat presentation, Working Party on Regional & Urban Statistics, 2007  Data availability and estimations by country in Urban Audit III 3 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

4. Netzwerk Stadt- und Regionalstatistik in Deutschland Federal Agency for Construction and Regional Planning BBR Federal Labour Agency BA with Institute f. Labour Market Research IAB Federal Statistical Office Statistical Offices of the States Statistics of the State:Municipal statistics: Association of German Municipalities with o Union of Municipal Statisticians o KOSIS Union Network  Among the more than 350 cities in the European Urban Audit: 40 German cities  Due to the federal structure of Germany, the Urban Audit is managed here by an association of the 40 cities, cooperating in a network with State Statistics. 2. The Urban Audit, as it is realised in the German environment 4 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

5.  The 40 German cities incorporate all capitals of the German Federal States, most large cities of more than half a million population, many with more than 250,000 and some additional smaller cities above 50,000 inhabitant.  As in all the other states, the following number of variables are requested: 250 for Germany as a whole 190 for the so-called Larger Urban Zone 340 for the cities in their administrative boundaries 50 for the sub-city districts  In addition, a reduced set of data is to be collected for all remaining 45 cities in Germany of more than 100,000 inhabitants. German environment continued: Content of the Urban Audit 5 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

6. 3. The problems that NSOs have with estimations The Urban Audit is a project of international comparison based on international definitions. 3.1 National definitions versus international definitions Many National Statistical Offices refuse, for principle reasons, to make estimations: They produce “official statistics”, and this is based on official national definitions. 3.2 Lack of data between census years The Urban Audit requests a comprehensive set of data. Many of them are only available from censuses. Other sources use other definitions or require disaggregation of more global sample results. 3.3 Differing reference years – tolerate or adjust? Differences of census years are tolerated. But many other sources require adjustments by estimation. Averages of several years are more easily accepted by National Statistical Offices than estimations where data are missing. 6 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

7. NSOs‘ problems with estimations continued 3.4 Data from sample surveys NSOs fill gaps between census years by sample surveys, which are representative only for larger areas. Disaggregation of these results requires estimations supported by auxiliary data. NSOs don’t normally make these estimations. 3.5 Data for areas that differ from the requested areas Some data do not refer to the administrative areas of the cities (examples: transport and waste collection). Adjustments require estimations, i. e. mostly a distribution in proportion to the population. 7 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

8. 4. Solutions discussed by Eurostat‘s group of experts (Think Tank) Collect the data only for census years and once in between  Planning requires up-to-date information thus enforcing estimations Reduce the number of variables to a small set of key variables  Reduction to key variables would prevent investigations into the causes of changes. Different users ask different questions. Estimate indicators instead of the basic variables  This would hide the causes of changes, whether caused by the numerator or by the denominator of the fraction expressed by the indicator. It would also cause a loss of transparency for the user. Have the estimates made by other institutions outside NSOs  This was finally recommended as an acceptable alternative to estimations by the NSOs. 8 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

9. 5. German estimations for the Urban Audit About 40 % of the data provided for the Urban Audit result from “estimations”. This comprises all kinds of calculations by which data are derived from the available data to comply with Eurostat’s requests and definitions. One reason for this high proportion is the lack of a recent census and therefore the great variety of data sources:  Regional Statistics of the Federal Statistical System  Micro-Census of the Federal Statistical System  Administrative register of the Federal Labour Agency  Administrative register of motor vehicles  Administrative register of the local / the Federal Criminal Police  NGO‘s for cultural statistics  The Cities‘ Statistical Offices 9 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

10. Central and decentralised estimates Where estimates for territorial transformation are necessary, they are left to the cities, because they dispose of the required auxiliary data. All SCD data provided by the cities must be adjusted to the prescribed definitions. These and all other estimates and adjustments to the prescribed definitions are done centrally by the NUAC or by contracted experts. German estimations for the Urban Audit continued 10 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

11. Categories of estimation 5.1 Disaggregation for Cities on a lower administrative level (below NUTS 3) 5.2 Adjustment of sub-city data (also: iterative adjustment of structures) 5.3 Simple translation into differently defined groups 5.4 Estimation of requested sub-city data by distribution in proportion to available auxiliary data 5.5 Estimation of very detailed data on employment and unemployment for the cities and Larger Urban Zones (combining Micro-census and register data) 5.6 Estimation of socio-economic data from the Microcensus German estimations for the Urban Audit continued 11 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

12.  There is no sub-city statistics from the Federal Statistical Office or State Statistical Offices. For sub-city statistics, Municipal Statistical Offices are the only source.  The SCD of the Urban Audit are not identical with the official statistical subdivision of the cities.  Estimates are therefore necessary for  the territorial transformation of the data, if SCD cannot be composed of the official districts of the city  for an adjustment to the prescribed definitions and harmonisation with the official city totals translations into differently defined groups SCD data from the German cities German estimations for the Urban Audit continued 12 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

13. Special case: Estimation procedure for households in sub-city districts 1. Excerpt from population register is sorted by postal address 2. „Households“ are generated by applying the German household generating model (developed in the KOSIS association) based on indicators for persons to belong to a common household 3. Generated households are adjusted to the total number of households in city as estimated from the Micro-census German estimations for the Urban Audit continued 13 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

14. 6. Documentation and metadata  Eurostat‘s detailed Glossary contains all definitions to be observed.  Eurostat‘s reference Guide informs the user on the actual data production and estimation procedures in the countries.  Each value is identified by a territorial code, a variable code and a reference year. Its data quality is indicated by a „Flag“, i. e. a combination of letters definded in the Glossary.  A detailed final report to be submitted by each National Urban Audit Coordinator provides the basis for the „Reference Guide“. The hope is that the NSOs will learn from each other and that national definitions can gradually be harmonised. 14 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

15. 7. Conclusions  The Urban Audit is to help understand structures and evolutions in the European urban system by comparison in order to make better urban planning, better development programmes and better political decisions.  Comparability is here a central requirements.  NSOs know their data best, they have the necessary methodology and tools. They should bring their data to the best possible use by making – or at least supporting – necessary adjustments and estimations for the intended international comparison.  Estimations require additional measures of quality assurance, especially a good documentation of the data sources and the methods applied. 15 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008

16. 16 Klaus Trutzel: Comparison through estimates Beijing Forum on Metropolitan Statistics 20-21 Oct.2008