ON THE FORMULATION AND COMPUTER IMPLEMENTATION OF AN AGE-DEPENDENT 2-SEX DEMOGRAPHIC-MODEL

A two-sex age-dependent demographic model is formulated within the fra mework of a stochastic population process, including both time-homogen eous and time-inhomogeneous laws of evolution. An outline of the param etric components of the system, which expedite computer implementation and experimentation, is also given. New features of the model include a component for couple formation, using the class of Farlie-Morgenste rn bivariate distributions to accommodate age preferences in selecting marriage partners, a component for couple dissolution due to separati on or divorce, and an outline of techniques for initializing a two-sex projection given scanty information. For the case of time-homogeneous laws of evolution, stability properties of two-sex models that are an alogs of those for one-sex models are difficult to prove mathematicall y due to nonlinearities. But computer experiments in this case suggest that these properties continue to hold for two-sex models for such wi dely used demographic indicators as period crude birth rates, period r ates of natural increase, and period age distributions, which converge to constant forms in long-term projections. The values of the stable crude birth rate, rate of natural increase, and quantiles of the stabl e age distribution differ markedly among projections that differ only in selected values of parameters governing couple formation and dissol ution. Such experimental results demonstrate that two-sex models are n ot merely intellectual curiosities but exist in their own right and le ad to insights not attainable in simpler one-sex formulations.