This paper provides a comprehensive assessment of the evolution of EU member states' power, the EU's capability to act (efficiency), and the proportionality of the voting system in the Council of Ministers from the treaties of Rome in 1958 till the Treaty of Lisbon in 2009 and beyond, using a wide range of alternative power indices. Moreover, it considers explicitly the relevance of additional legal provisions (such as the 'Luxembourg Compromise', the 'Demographic Clause', and the 'Ioannina Compromise') and the implications of novel, more recently introduced voting rules such as reverse qualified majority voting. (authors' abstract) / Series: Department of Economics Working Paper Series