In this paper we study the global stability properties of both descriptive and optimally controlled economic systems possessing inherent non-linearities. Stability conditions for these non-linear models are established, and a complete characterization of the dynamic path is obtained. Moreover, the relationship between the global stability properties of descriptive and optimal control models is clarified, the trajectories of descriptive models are compared with those of the planning models and conditions are examined under which the behavior of completely stable descriptive models approximates optimal solutions. © 1975.