1. Department of Sociology and Social Work, OPIK, University of the Basque Country, Leioa, Spain
2. Ikerbasque, Basque Foundation for Science, Bilbao, Spain
3. Population Research Centre, Faculty of Spatial Sciences, University of Groningen, Groningen, the Netherlands
4. Centre for Demographic Research, Université Catholique de Louvain, Louvain-la-Neuve, Belgium