Complexity and agent based models in the policy process

Rosewell and Ormerod have collaborated for over a decade in Volterra Partners, building models using complexity principles for clients in the public and private sectors. We present examples of agent based models commissioned by policy makers and used as inputs into the decision making process. We discuss problems which arise within both public and private sectors when a complex modelling approach is proposed. For example, the standard approach to policy analysis, that of economics, has the advantage in that it often purports to give the right answer. Complex systems modelling in contrast emphasises uncertainty of outcome. The paper describes the way in which policy makers describe and identify problems, how they can be engaged, how they can `buy in´ to the results of a model, how to involve the decision maker in the validation of the model. These points are illustrated from actual models which have been built in practice.