This study has been prepared within the UNU-WIDER project on 'New Approaches to Measuring Poverty and Vulnerability', directed by Jukka Pirttilä and Markus Jäntti. This paper is reproduced here by permission of UNU-WIDER, who commissioned the original research and holds copyright thereon. UNU-WIDER gratefully acknowledges the financial contributions to the research programme from the governments of Denmark, Finland, Sweden, and the United Kingdom.