This paper describes the economic module used in the IIASA/UNFPA Mauritius Project. The Project developed a population-development-environment (PDE) model which includes a demographic, an economic, a land use, and a water module. The economic is an input-output model, a choice which reflects the need to distinguish a larger number of economic sectors when looking at the interaction of the economy with the population and the environment. The model is set up to function for a small, open economy. It seeks a household consumption and income equilibrium, and an investment and savings-plus-loans equilibrium. It distinguishes three income groups by level of education with different consumption patterns depending on the level of income. It includes labor productivity changes resulting from a changing educational structure of the labor force.