Acknowledgements
The authors would like to thank many people for helpful comments on previous drafts including Anna Dixon, Jonathan Hopkin, Lorelei Jones, Lucie Kalousova, Deborah Mabbett, Minakshi Raj, Holly Holder, Mauricio Avendano, Raphael Wittenberg, participants in panels at the European Public Health Association Conferences in Ljubljana and Marseille and a workshop at the University of Wales Bangor.