The paper summarises different patterns of differentiation and reintegration in core state powers during the post-Maastricht period, based on the EUDIFF-RES dataset. Moreover, it offers a theoretical framework able to explain the observed variation. The framework is further tested by means of short empirical illustrations taken from different policy areas. Overall, the EUDIFF-RES dataset substantially contributes to our understanding of CSP differentiated integration by revealing that the behaviour of states vis-a-vis core state powers varies greatly according to the kind of resource, as well as the costs and opportunities attached to it
