Principles of social exchange and Heider's balance theory are combined to arrive at a predictor variable called an “exchange ratio.” Two actors and an exchange item are treated as a three-point structure consisting of three dyads. Two dyads connect each person to the exchange item. The third dyad represents the degree of balance between the two actors as derivable from an examination of their inputs and outcomes vis-à-vis the exchange item. The model is expanded to treat relationships consisting of several exchange items as complex structures made up of overlapping three-point structures. The resulting “exchange ratio” is a value representing the composite balance or imbalance in the exchanges of a relationship.