Strucural change and DSGE models

In most existing DSGE models, parameters are supposed constant and exogenous shocks have zero mean. This makes difficult to treat structural change and anticipated effects of future reforms. Introducing dummy variables in the DSGE model can only handle unexpected changes. This papers deals with upcoming changes supposed to be known, at least to some extend, by all agents such as, for example, demographic change or adhesion to the euro in European accessing countries. The modelling device used in the paper is to introduce future values of deterministic exogenous variables among state variables upon which agents make their decision. Illustration of the procedure is provided for simulation with approximations at order 1 and 2 and for estimation of linear approximations.