The trio Presidency function entails that Member States in groups of three are responsible for drawing up a common programme for the Council for a period of 18 months and for assisting each other. This article contributes new knowledge by focusing on the variation between four different trio Presidencies that have ended their terms since the function was launched in 2007. A typology is developed to classify past and future trio Presidencies. It is shown that there are considerable variation between past trio formations with regard to whether they follow the same objectives (scope) and how much they co-ordinate to achieve these (depth). The observed variation is linked to the environment in which the trio Presidency operates, the individual trio members' attitude toward European integration, their territorial structuring of the state, their size, the ideology of the government and personality of the involved actors.
Jensen, M. D., & Nedergaard, P. (2014). Uno, Duo, Trio? Varieties of Trio Presidencies in the Council of Ministers. Journal of Common Market Studies, 52(5), 1035-1052. https://doi.org/10.1111/jcms.12130