The model is completed with the projection rules and the choice of closure.
The projection rules can be of different types: some of them are behavioral
relationships, such as the import equation or the money demand function; others
are simple rules that link the time path of a certain variable (e.g., government
transfers to the private sector) to that of a relevant 'scale' variable (such
as GDP). Finally, some variables (e.g., the world interest rate) are entirely
exogenous, in the sense that their assumed future evolution is not affectod by
any other variable in the model.