Through the work of Blalock [1] and Duncan [7], sociologists were introduced to the practice of building recursive models of interdependencies among several variables and to the use of path analysis to provide a flow graph representation of such models and to interpret their estimation. This type of formalization proved to be particularly useful in the representation of the socioeconomic life cycle (see, e.g., Blau and Duncan [2]; Duncan et al [10] ) as well as in many other areas of sociology. Not only is this class of models widely used in current sociological research, but most of its known statistical problems have been resolved. 1