Variations in sex ratios estimated from census and survey data in Zambia, 1969-2014

The sex ratio question has been an area of growing interest in population dynamics, especially in developing countries with respect to the issue of missing women, but few studies have examined this in sub-Saharan Africa. Both at birth and in the general population, sex ratios follow an expected demographic pattern in the absence of the interference of historical events affecting either males or females in a population. In Zambia, an unexpected demographic pattern of sex ratios is exhibited in census and survey data. This study used data from censuses and surveys conducted from 1969 to 2014 to examine variations in sex ratios in the Zambian population. It was found that sex ratio imbalances were largely due to data deficiencies due to age misreporting and under-enumeration. A consistent under-enumeration of young adult males in the 20-34 years age group was found. A systematic pattern of high sex ratios, above 100, for ages 40+ was found, represented by synthetic cohorts traceable from the 1969 census, progressing to the 2000 census and phased out in the 2010 census. Extremely high adult male mortality was found in 2010 in the 35-59 years age group, primarily attributable to HIV/AIDS. Understanding the demographic pattern of sex ratios in a population is relevant for policies to improve the quality of data collection systems, and socioeconomic development planning, for the young age group population, which is prone under-enumeration.