Migration, important for many areas in development, is strongly related to employment. Debate over labour supply in developing countries frequently hinges on labour migration. This paper examines the determinants of spatial mobility of working-age adults in South Africa, using the first nationally representative longitudinal survey – the National Income Dynamics Study – for 2008–10. The paper outlines the unique advantages of these data for the study of individual mobility – data that open the possibility of a new research project. Specifically, it asks how policy-relevant programmes, such as social transfers and housing assistance, affect migration. This paper finds, on balance, that transfers are negatively correlated with subsequent relocation. Previous migration is also predictive of future migration and both are tightly related to attrition, while there is an increasing but strongly non-linear relationship between income and mobility. Further, we highlight potential pitfalls – including attrition, and definitional difficulties – in the study of migration and illustrate possible solutions.