Age-specific sex ratios: Examining rural-urban variation within low- and middle-income countries.

The balance of men and women in society, captured by sex ratios, determines key social and demographic phenomena. Previous research has explored sex ratios mainly at birth and up to age five at national level, whereas we address rural-urban gaps in sex ratios for all ages. Our measures are based on the United Nations data on rural and urban populations by age and sex for 112 low- and middle-income countries in 2015. We show that rural sex ratios are higher than urban sex ratios among children and older people, whereas at working ages, urban areas are dominated by males. Our analysis suggests that the urban transition itself is not driving the gap in rural-urban sex ratios. Rather, internal migration seems to be key in shaping rural-urban sex ratio divergence in sub-Saharan Africa, while both internal migration and mortality differentials appear to be the predominant mechanisms driving sex ratio gaps in Latin America.