Dynamic specification and misspecification in systems of demand equations: a testing strategy for model selection

The purpose of this study is to describe a misspecification testing strategy that is designed to ensure the appropriateness of the statistical assumptions underlying a system of equations. A systemwise test approach is used to test the statistical assumptions. The systemwise tests take into account information in, and interaction between, all equations in the system and can be used in a wide variety of applications where systems of equations are estimated. If the systemwise test leads to rejection, single equation F-test will then be used to help identify specific problems. The systemwise testing approach is illustrated by modelling Swedish consumer demand for milk. The example illustrates how the approach can be used to solve issues regarding dynamic specification of models, structural change and other forms of model misspecification.