This paper presents a detailed examination of the European Union’s (EU) statistical sphere by investigating the impact of EU and national actors on the harmonisation of migration statistics. The main aim of this paper is to provide insight into the interplay of different EU institutions as well as the cooperation between national and EU institutions in the field of 'statistical governance', a policy area that EU scholars have so far neglected. Moreover, this paper uses theoretical notions of Europeanisation and governance to highlight the theoretical challenges of analysing statistical governance. Comparable quantitative data are essential for informed decision-making, particularly if this decision-making is aimed at a multiplicity of states - as it is the case in the EU. Yet, statistical components vary significantly between EU member states (MS) which not only hampers data comparability, but also limits the effectiveness of EU policy-making. It is therefore vital to shed light upon those who collect data and produce statistics. In the EU, these actors are fused in the European Statistical System, comprising the EU Statistical Office ‘Eurostat’ and the MS’ National Statistical Authorities (NSAs). The NSAs remain responsible for data collection and deliver their data to Eurostat which then produces EU-wide statistics. Migration statistics are distinctive among EU statistics as harmonised definitions are only obligatory for 2009 data onwards. In order to understand the process of data gathering and aggregation in practice, the cooperation between the British NSAs and Eurostat is examined. Document analysis and elite interviewing are used to trace decision-making processes within the British NSAs and Eurostat in order to study their impact on EU migration statistics.
