Mixed qualitative calculus as a tool in policy modeling: A dynamic simulation model of urban decline

Qualitative calculus of policy models is an appropriate method for policy impact analysis in the case of imprecise information concerning the structural model parameters. The conditions of the so-called sign-solvability analysis of a linear equation system—with information represented by a positive, negative, or zero impact—are strict, however. In this paper, the relevance of qualitative calculus for urban policy modelling is discussed. An extension of the sign-solvability approach (with purely qualitative information) will be dealt with in the case of a mixture of qualitative and quantitative information. We introduce the use of matrix decomposition methods, of theoretically plausible parameter restrictions, and of a top-down/bottom-up approach for sign-solvability. The sign-solvability approach is applied to a dynamic policy simulation model of urban decline in The Netherlands, developed for the city of The Hague. Given the insufficiently reliable database for estimating the model in a conventional econometric way, qualitative calculus was used in order to infer conclusions regarding the direction of impacts of policy variables.