Over the past decades, many different kinds of models have been developed that have been of use to policy makers, but until now the different approaches have not been brought together with a view to enhancing the systematic unification and evaluation of these models. This new volume aims to fill this gap by bringing together four decades' worth of work by S. I. Cohen on economic modelling for policy making. Work on older models has been rewritten and brought fully up to date, and these older models have therefore been brought back to the fore, both to assess how they influenced more recent models and to see how they could be used today.