The two-sex problem with persistent unions: a generalization of the birth matrix-mating rule model.

The birth matrix-mating rule (BMMR) model solves the two-sex problem of classical stable population theory by allowing births to adjust to changes in a population's age-sex composition. To avoid complications the BMMR model assumes that unions last for only a single period. This paper drops that assumption and presents the BMMRPU (BMMR persistent unions) model. To establish the existence of equilibrium in the BMMRPU model, the existence proof used in the BMMR model is supplemented by a fixed-point argument.