Abstract
The volume of data being produced for administrative purposes is increasing rapidly. Data must be analysed in order to extract useful information to support decision making. The demand for evidence-based information means that the analysis must be conducted according to the principles of scientific research. Unfortunately, the massive second-hand data sets seem not to fit very well into the traditional methodological paradigm. A secondary data source imposes limitations on the formulation of a problem and concepts, because the measurement can only be based on existing data. The aim of this paper is to present a methodological framework for the utilisation of administrative registers in the creation of scientifically valid information. This is done by discussing fruitful methodological aspects encountered in the practical knowledge-discovery process. The ideas presented originate from many different fields, such as statistics, data mining and sociology. The emphasis lies on understanding connections between problem, data and analysis in the case of massive secondary administrative data sources.