Some methods of qualitative structural analysis, as MFA, are based on the analysis of layers (flow matrices generated at each iteration when the equilibrium of an input-output model is computed). MFA mixes the analysis of the pure structure of production (the technical coefficients) and of the final demand. I have demonstrated that all column-coefficient matrices (or row-coefficient matrices) computed from each layer are the same in MFA: the information brought by one layer is identical to those of another layer. For a given structure of production, the only element of variability over layers is caused by the flows that final demand generates.If the new definition of layers proposed by the creators of MFA is adopted, the method becomes similar to a quantitative method of structural analysis.