M-labeled digraphs are defined and a technique for determination of the sign of sequences in such digraphs is presented. Conditions under which the sign of a sequence can be determined are derived. This work is motivated by the need to assess the structural effect of an “input” upon the endogenous quantities of an M-labeled digraph. A technique for comparing and combining the effects of structurally redundant inputs is presented. The theoretical development is followed by application to a prototypical Forrester model involving a population sector interactant with a housing sector.