The problem of improving the quality of governmental strategic planning and forecasting is considered. It is assumed that the model of the controlled system for designing managerial decisions is constructed in the course of the so-called system research. Mathematical models of this process, strategic decision-making and their impact on social welfare are developed in order to analyze the impact of the organization of system research on the quality of the resulting model and also on the quality of strategic managerial decisions. For this purpose, the construction procedure of the estimated social utility function is described. The accuracy and quality of managerial decisions based on maximizing this function are formalized. The robustness conditions of the controlled system (enterprise, industry, national economy) with respect to the distortions of the social utility function and optimal policy are described. The expected number of factors taken into consideration from all potentially significant factors depending on the number of experts engaged in system research is determined. As a result, the minimum admissible number (threshold) of experts required for constructing an adequate model of the controlled system is estimated. The model is simulated using the Monte Carlo method in MatLab.