Planned introductions of genetically modified crop varieties can be troublesome to model. Estimation of demand and supply equations is not feasible due to lack of data. Further, specifying demand and supply equations requires calibration to a presumed equilibrium. Depending on the point chosen, highly questionable results may be obtained. We propose a model that uses existing supply, demand, and elasticity estimates. The approach relies on composite supply and demand functions. These composite functions are linear combinations of GM and non-GM varieties. We then employ this approach in a model of world wheat trade to analyze the impact of several plausible GM wheat adoption and consumer acceptability scenarios.