Acknowledgments: We are grateful to Celine Azemar, Ron Davies, Rodolphe Desbordes, Hartmut Egger, Holger Görg, Michael Moore, Ali Naghavi, Peter Neary, Pascalis RaimondosMÞller, Ian Wooton and two anonymous referees for useful comments and suggestions. The usual disclaimer applies.Peer reviewedPublisher PD