Sex ratio at birth and son preference

In a population with a strong preference for sons, significant fertility decline is often accompanied by a considerable increase in the population sex ratio at birth (SRB, usually recorded as the ratio of the number of male births to the number of female births; Bennet, 1983; Zeng et al., 1993; Park and Cho, 1995), leading to a projected imbalance in future first-marriage ratios (Tuljapurkar et al., 1995; Park and Cho, 1995). The purpose of this paper is to examine the relationship between son preference and SRB. We are particularly concerned about sex selection for sons, by which we mean active intervention (by sex-selective abortion, infanticide, abandonment, or other actions with similar consequences) at a particular birth to ensure that the child is male. Why does fertility decline cause an increase in SRB? When fertility is high in any population, there are few families with no son. Also,