Multiregional and Intertemporal Age Modelling Via GEMPACK

The past few years have seen increasing use of multiregional and intertemporal (that is, forward-looking) applied general equilibrium (AGE) models. These models share the characteristic of rapidly expanding dimensions. Because multilateral trade models increase in size with the square of the number of regions and intertemporal models increase in proportion to the number of time periods, they can be very difficult to solve purely because of their size. This paper considers three recent models of these kinds, namely, GTAP, the Global Trade Analysis Project's multiregional model of the world; MRES, a multiregional forecasting model of Australia; and ORANI-INT, an intertemporal model of the Australian economy. Each of these has been implemented using the GEMPACK suite of general-purpose economic modelling software. In this paper we discuss features of GEMPACK which are especially relevant for multiregional and/or intertemporal models. These include an automatic facility to condense models to a manageable size; separation of theory, data, and closure/shocks; automatic creation of updated (that is, post-simulation) data files; and a solver that is well suited to intertemporal models with substantial elements of forward-looking behaviour. Each feature is illustrated via references to one or more of the three models mentioned above.