In 2008, the Common Agricultural Policy (CAP) reached its fiftieth birthday. It has been a constant factor in directing resources to the EU agricultural sector, but the means of channelling these resources have changed considerably over time. This article charts the evolution of the CAPs principal policy instruments and analyzes the welfare effects of its major reforms. It also analyzes these changes in terms of the institutional context of the principal reform pressures, namely international trade obligations and EU budget concerns. We will show that the link between these two pressures was never one of simple determinism: the CAP and its reform can only be understood in light of these pressures and of endogenous vested interests to the policy.