15  Cottarelli, C. and Guerguil, M. (eds. ), Designing a European Fiscal Union: Lessons from the Experience of Fiscal Federations, Routledge, 2014. 16  In particular, the economic literature uses as a criterion the comparison between, on the one hand, the heterogeneity of preferences and situations and, on the other, the externalities linked to different policies.
It also highlights the need for a dynamic approach to take into account the economic and political factors of convergence and divergence. See, in particular, Alesina, A. and Wacziarg, R., “Is Europe Going Too Far?”, Journal of Monetary Economics, Carnegie-Rochester Conference Volume, 1999, pp.