Introduction to Special Issue: Matters of classification and representation: Quantifying ethnicity, religion and migration introduction

In addition to serving as an introduction to the subject, this paper suggests a conceptual framework for the investigation of issues of classification and quantification related to migration and the ethnically and religiously diverse societies in Europe. Nationality, ethnicity and religion are situational, contextual and dynamic social phenomena which tend to defy rigid classification, making it especially difficult to capture and quantify these entities in order to organize and represent them in an intelligible manner in official statistics (e.g. censuses), institutional governing practices or in academic survey research. By drawing on previous work by demographers and social researchers, we suggest a typological classification of ways in which diverse populations become statistically visible or invisible. We show that the rationale for creating classifications and particular sets of categories changes, depending on the political field in which data are used in the governance of populations and migration. A science studies perspective can make these diverse taxonomies the object of studies to understand how they are embedded within, and how they sustain, power relations. By focusing on practices of classification as instruments of research and governance, this special issue contributes to a reflection on the conditions and effects of quantifying practices in culturally diverse and constantly changing societies, in which the line between government and academia, between power and knowledge, is frequently indistinct