- Correspondence to L Tarkiainen, Population Research Unit, Department of Social Research, University of Helsinki, P.O. Box 18, Helsinki FIN-00014, Finland;
- Accepted January 24, 2011
- First published March 4, 2011.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.