Data on how patterns of migration to Europe have developed. The THEMIS international project team investigated what makes people decide to migrate; why some of those initial moves to Europe result in the formation of significant migration systems; and why some migration processes simply tail off or stagnate. This involved a comparative study of the evolution of migrant groups following different migration trajectories from several regions of three origin countries (Brazil; Morocco and Ukraine) to selected areas in four destination countries (UK; Norway; the Netherlands and Portugal).