1. Department of Social Research; University of Helsinki, PO Box 18 (Unioninkatu 35); 00014 Helsinki Finland
2. Department of Political and Economic Studies; University of Helsinki; Helsinki Finland
3. Department of Social Research, University of Helsinki, Helsinki, Finland; Centre for Health Equity Studies (CHESS), Stockholm University; Karolinska Institutet, Sweden; and the Max Planck Institute for Demographic Research, Germany