In this paper, the relationship between the assumptions in the supply-driven and the demand-driven input-output model is discussed. A necessary and sufficient condition is given for the stability of the input coefficients, the output coefficients, and both coefficients. For both models, the effects of a demand pull on the total outputs and on the primary inputs are analytically expressed. Also, the effects of a supply push on the total outputs and on the final outputs are expressed, again for both models. In general, the assumption of fixed input coefficients in the demand-driven model does not hold, but computations are still based on it. A necessary and sufficient condition is given for the correctness of the computed total outputs, both for a demand pull and a supply push. Similar results are obtained for the supply-driven input — output model.