Page 1 of 3 Next  Paul Norman School of Geography University of Leeds Woodhouse Lane, UK p.d.norman@leeds.ac.uk Abstract In the UK there has been a large expansion in the availability of spatially referenced Census, Vital Statistics and administrative data over the last few decades. This has been paralleled by increases in computer power, the sophistication of analysis packages and of programmer and user skills. To investigate trends and identify change over time we need data consistent in definition over time and space. Unfortunately, a variety of technical issues need to be overcome before even a rudimentary analysis can be carried out. Attribute data may vary over time in terms of topic availability, definition and the demographic detail for which variables are released. Similarly, the geography for which data are available may change through time either due to a decision about the geographic scale of release or because a boundary change has occurred. These difficulties are compounded by the variety of geographies for which data may be disseminated. For time-series analysis, harmonisation of both attribute and geographical information is essential. In this paper some examples of problems and solutions are given. 1. Introduction In the UK there has been a large expansion in the availability of spatially referenced sociodemographic data over the last few decades. This has been paralleled by increases in computer power, the sophistication of analysis packages and of programmer and user skills. The UK’s decennial Census provides detailed sociodemographic information from national to local level. Censuses enable descriptions of population size and characteristics and the calculation of, for example, rates of illness or unemployment by population sub-group and local geographies. We also have high quality information on births and deaths from the Vital Statistics (VS). The VS have been available annually since the 1980s in computerised formats and underpin the calculation of fertility and mortality trends (Rees et al. 2003). We have little information, however, about movements over the life-course due to a paucity of subnational and international migration data since we do not have national registration, unlike Scandinavian countries and the Netherlands. The application of demographic methods help us study population structure and the components of change. Demographic techniques can reveal inequalities between population sub-groups (by sex, ethnic group or social class, for example) and between locations. To investigate trends and identify change over time we need data consistent in definition over time and space. Unfortunately, there are a variety of issues to be overcome before even a rudimentary analysis can be carried out. Relating to attributes these problems include: changes in the questions asked and the definitions and classifications used and changes in tabulations. In relation to geography, problems include: changes in the scale and type of areas for which data are disseminated and changes in the boundaries of areas for which data are available (Norris and Mounsey 1983). This paper will first illustrate issues regarding inconsistencies in attribute information over time with some harmonisation solutions identified which researchers might consider using. In the following section, the harmonisation of geographical boundary systems over time is discussed. The overall aim of the paper being to act as a resource for researchers entering this area of research. The issues and techniques being discussed here are being investigated and applied during ongoing demographic research (Norman 2006). 2. Harmonisation of attribute information Demographic data have been available from the Registrar General’s decennial reports since 1851 (the legal requirement to register births and deaths began in 1938). Vital Statistics on births and deaths have been available annually in computerised formats since 1981 at various geographic scales. Inevitably, an analysis of a sociodemographic time-series will rely on the UK’s decennial censuses which have been collected since 1801 and in computerised formats from 1971. Thus the main focus here is on sources that will help the researcher disentangle inconsistencies in attribute information available in the censuses. Conceptually the challenges of a time-series of births and deaths data are more straightforward but compatibility cannot be assumed.
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