Source: Based on Frank Schimmelfennig, Good Governance and Differentiated Integration: Graded Membership in the European Union. European Journal of Political Research 55: 4, 2016, 789-810.
Grades of membership
Most maps of the European Union only distinguish between member and nonmember states – a blue mass in the heart of the continent surrounded by white space and a few white spots like the micro-states, Switzerland, and the Kaliningrad area in between. But Europe is much more colorful. Differentiated membership in the EU and its policy regimes comes in a variety of grades – both for formal members and formal nonmembers. Each color in the map represents a different grade of membership. There is still a blue mass – the core of member states participating in all integrated policy regimes of the EU at the highest level. Some member states – such as the non-euro area countries – do not belong to the core, whereas all nonmember states have some kind of association with the EU. The UK is about to give up its differentiated integration within the EU and replace it with some form of differentiated integration outside the EU.