The Governing Council is the highest decision-making body of the ECB, consisting of executive board members and governors of the national central banks. Apart from the fundamental notion of joint responsibility, two guiding principles of the Treaty determine the operational side of the System. First, subsidiarity prescribes that the responsibilities lie at the lowest possible level.
In the context of the European Community, this principle respects national sovereignty and reflects the heterogeneity of its Member States. Second, the Treaty prescribes an efficient allocation of resources. In other words, the System should be effective at the least cost. In practice, there may be trade-offs between the principles of subsidiarity and efficiency, but gross inefficiencies should, of course, be avoided.