Data visualisation in migration research: the case of circular migration plots

Human migration between countries or regions is difficult to visualise using standard tools for spatial data analysis or geographical information systems. A conventional approach has been to show migration flows as stroked lines drawn atop a geographic map. But overlapping arrows limit flow maps in their capacity to show variation in the size of flows as well as larger numbers of flows within world regions such as Europe. Circular migration plots are a viable alternative to conventional flow maps and other existing visualisations of migration flows. Circular plots are an effective and visually appealing method for visualising flow data because they allow the reader to quickly identify key patterns and trends. This chapter introduces circular migration plots and provides readers with the necessary tools and information to efficiently visualise human migration themselves. We demonstrate the wealth of information that circular migration plots visualise by presenting their key features. We further provide guidance in ensuring readability and reducing the risk of misinformation by making appropriate design choices, which mainly relate to the reduction of clutter and designing colour-blind friendly plots. We conclude by arguing that circular migration plots make it easier to graphically evaluate complex patterns and trends in migration flow data, and to inform scientists in other disciplines and the general public about human migration.