In this paper, we document the Simplified International Model of agricultural Prices, Land use and the Environment (SIMPLE). SIMPLE is a partial equilibrium model which is designed to better understand the competing forces that influence the global farm and food system and how these drivers influence long run agricultural land use, production, prices, GHG emissions and food consumption. SIMPLE has been developed under the principle that a model should be no more complex than is absolutely necessary to understand the basic forces at work. Therefore, unlike other global models which are generally more complex and disaggregated, SIMPLE is parsimonious and tractable. Indeed, our historical validation over the period 1961-2006 confirms that SIMPLE can be used to simulate the long run changes in the global farm and food system given exogenous shocks in a few key drivers of world agriculture. Equally important is that we demonstrated how SIMPLE can be used to assess the relative contribution of each of the individual drivers to the endogenous changes in world agriculture via the numerical and the analytical decomposition tools. With these tools at hand, SIMPLE offers a more robust analysis of both historical and future long run changes in the global farm and food system.