The paper describes historical and decomposition simulations of the Australian economy undertaken with the MONASH model. The simulations cover the period 1996/97 to 2001/02. The paper first describes the historical simulation. In the historical simulation, many of the sectoral variables in MONASH representing observable features of the economy are determined exogenously at their observed historical values. This allows the model to calculate the outcomes for sectoral variables describing (typically unobservable) features of the economy's structure, such as industry production technologies and household tastes. The estimates for these structural and taste variables play a key role in explaining the observable features of the economy over the study period. To isolate the contribution of each of these structural features to observed economic outcomes, they are fed back into the model as exogenous shocks in the decomposition simulation. The decomposition simulation is then used to explain the causes of major changes in the Australian economy over the period 1996/97 - 2001/02 in terms of changes in technologies, tastes and other structural variables.