Although improvements in agricultural production have occurred and malnutrition has declined at the global level since the 1960s, serious questions remain about the ability of world agriculture to continue to realize significant increases in developing-country food availability into the 21st century. With suitable arable area throughout much of the world already under crop production and the advancements of the Green Revolution essentially complete, agricultural research and development will be an increasingly crucial variable affecting future food production increases, and contributing to improved food security. Since the early 1990s, the Special Project Global Trends in Food Supply and Demand has used the International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT) to address these questions and examine alternative futures for global food supply, demand, trade, prices, and food security.

IMPACT covers 32 commodities (which account for virtually all of world food production and consumption), including all cereals, soybeans, roots and tubers, meats, milk, eggs, oils, meals, vegetables, fruits, sugar and sweeteners, and fish in a partial equilibrium framework. It is specified as a set of country-level supply and demand equations where each country model is linked to the rest of the world through trade. In order to explore food security effects, IMPACT projects the percentage and number of malnourished preschool children (0 to 5 years old) in developing countries as a function of average per capita calorie availability, the share of females with secondary schooling, the ratio of female to male life expectancy at birth, and the percentage of the population with access to safe water.

A wide range of factors with potentially significant impacts on future developments in the world food situation can be modeled based on IMPACT. They include: population and income growth, the rate of growth in crop and livestock yield and production, feed ratios for livestock, agricultural research, irrigation and other investments, commodity price policies, and elasticities of supply and demand. For any specification of these underlying factors, IMPACT generates projections for crop area, yield, production, demand for food, feed and other uses, prices, and trade; and for livestock numbers, yield, production, demand, prices, and trade.

The model has been continuously revised to include additional commodities and greater regional disaggregation and the base year updated. During 1998-2000, the IMPACT-WATER model was developed, which combined the IMPACT model with the Water Simulation Model (WSM) in order to estimate the interactions between water supply and demand and food supply, demand, and trade. New advancements for the suite of IMPACT models (including IMPACT and IMPACT-WATER) include a greater level of spatial disaggregation, the inclusion of additional crops, and an update of the base year to the year 2000. While the primary IMPACT model divided the world into 36 countries and regions, the IMPACT-WATER model uses a finer disaggregation of 69 basins out of recognition of the fact that significant climate and hydrologic variations within regions make the use of large spatial units inappropriate for water resource assessment and modeling.