Conventionally, system-wide approaches to regional economic modelling have been exclusively demand-oriented. A major distinguishing feature of the current volume is the attempt by a number of contributors to model the supply-side. Developments in the two traditional system-wide approaches to regional economic modelling, namely input-output and macro-economic modelling, are examined. Additionally, an account of the emerging "computable general equilibrium" framework is provided and its weaknesses and strengths are discussed. The author attempts to provide an account of why policies were formulated and implemented in the way they were, and to establish how they were implemented as well as to what effect - both intended and unintended.