This paper presents the methodology as well as the results of the joint OECD-European Commission project Migration-Demography Database: A monitoring system of the demographic impact of migration and mobility. The objective of the project is to evaluate the contribution of migration to past and future labour market dynamics across EU and OECD countries. After assessing the role of migration over the last five to 10 years in shaping the occupational and educational composition of the labour force, this project looks at the potential contribution of migration to the labour force in a range of alternative scenarios. This paper presents the results from the second part of the project: it focuses on projections over the period 2015-2030, and aims at identifying the drivers of changes in working-age population and active population in European countries, and in particular the role of migration flows.