Exploring the population implications of male preference when the sex probabilities at birth can be altered

Objective: The paper explores the population effects of male preference stopping rules and of alternative combinations of fertility rates and male-biased birth sex ratios. Methods: The ‘laboratory’ is a closed, stable population with five age groups and a dynamic process represented by a compact Leslie matrix. The new element is sex-selective abortion. We consider nine stopping rules, one with no male preference, two with male preference but no abortion, and six with male preference and the availability of abortion to achieve a desired number of male births. We calculate the probability distribution over the number of births and number of male births for each rule and work out the effects at the population level if the rule is adopted by all women bearing children. We then assess the impact of alternative combinations of fertility rates and male-biased sex ratios on the population. Results: In the absence of sex-selective abortion, stopping rules generally have no effect on the male/female birth proportions in the population, although they can alter the fertility rate, age distribution, and rate of growth. When sex-selective abortion is introduced the effect on male/female proportions may be considerable, and other effects may also be quite different. The contribution of this paper is the quantification of effects that might have been predictable in general but which require model-based calculations to see how large they can be. As the paper shows, they can in fact be very large: a population in which sex-selective abortion is widely practised can look quite different from what it would otherwise be.