A framework for combining extraneous information with an econometric model to evaluate the economic impacts of pesticide withdrawals is presented in this paper. The extraneous information, which can be a best guess or experimental data, is used to shift an econometrically estimated supply function. The full sectoral econometric model is then simulated through time with and without the supply shift to estimate the relative impacts of withdrawing the pesticide. The theoretical framework is applied to the withdrawal of all insecticides used on cotton.