In recent years, migration statistics have played a prominent role in debates about the scale, nature and impacts of immigration to the United Kingdom. This paper, written by a ‘consumer’ of migration data, focuses on the interface between migration statistics, public policy making and public discourse.\n\nNothing demonstrates the importance of this nexus better than debates in the UK about the impact of the latest round of European Union enlargement. In the months leading up to 1 May 2004, considerable public attention was paid to the apparently large numbers of migrants who were expected to ‘flood’ in to the UK. Official estimates were accused of underestimating potential flows and impacts, and the Government was pressured to reconsider allowing free mobility of workers.\n\nIn the event, the Government resisted this pressure but settled on a scheme that required migrant workers to register. Data collected from the 176,000 applications lodged between 1 May 2004 and 31 March 2005 have been invaluable to researchers and policy makers trying to understand the impacts of intra-EU mobility.\n\nThis experience should be seen a wider context in which inadequacies in and controversies about data on the scale and impact of immigration (eg the number of irregular migrants and the fiscal impacts of immigrants) have hampered policy development and led to unhelpful debates. The evidence base for policy making is far from complete, policy measures are hard to justify, scaremongering claims are hard to refute and general confidence in governance is hampered. This paper suggests that collecting more robust data and presenting it in accessible forms will be a critical first step in managing migration and managing debates about migration.