Determinants of the sex ratio at birth: Review of recent literature

Abstract This paper reviews recent literature on the determinants of the sex ratio at birth. The first part provides an overview of the major findings on the biological determinants, and their implications on the racial differentials and the wartime increases in the sex ratio at birth. The second part discusses the sociodemographic factors of the sex ratio at birth (age of parents, birth order, and socioeconomic status). About thirty studies based on samples of millions of births drawn from national vital registration statistics in various countries are reviewed and compared. The results indicate that birth order and paternal age appear to be negatively correlated with the sex ratio at birth. Parents of higher socioeconomic status may be more likely to bear sons than parents of lower socioeconomic status. Some possible causal mechanisms are suggested for the effects of the sociodemographic factors.