This volume originated in conversations among friends and colleagues more than 10 years ago. In its early days our work was supported through the EQUALSOC “Network of Excellence” funded by the European Union. Latterly we have received financial support in bringing this project to fruition from our home institutions, Nuffield College, Oxford and the University Mannheim. There are many other institutions to whom we owe a debt of gratitude. Yale University supported Richard Breen’s research for much of the period during which we were working on this topic and we, as individuals and as groups of authors, have benefitted from the hospitality of the Wissenschaftszentrum Berlin; Tilburg University; the University of Trento; the European University Institute, Florence; SFI (the Danish National Centre for Social Research), Copenhagen; and Sciences Po, Paris. Parts of this book have been presented at seminars, workshops and conferences in the US and Europe and at meetings of Research Committee 28 (Social Stratification and Mobility) of the International Sociological Association, and the annual conference of the European Consortium for Sociological Research. We thank the participants on all these occasions for their criticisms, thoughts, and suggestions. Lastly our thanks go to Beate Rossi in Mannheim and Maxine Collett and Kayla Schulte in Oxford for their help in finalizing the manuscript.