Human sex ratio

In anthropology and demography, the human sex ratio is the ratio of males to females in a population. Like most sexual species, the sex ratio in humans is approximately 1:1. The sex ratio at birth worldwide is commonly thought to be 107 boys to 100 girls, although this value is subject to debate in the scientific community. The sex ratio for the entire world population is 101 males to 100 females. Depending upon which definition is used, between 0.1% and 1.7% of live births are intersex.

Gender imbalance may arise as a consequence of various factors including natural factors, exposure to pesticides and environmental contaminants, war casualties, gender-selective abortions and infanticides, aging, and deliberate gendercide.

More data are available for humans than for any other species, and the human sex ratio is more studied than that of any other species, but interpreting these statistics can be difficult.

Human sex ratios, either at birth or in the population as a whole, are reported in any of four ways: the ratio of males to females, the ratio of females to males, the proportion of males, or the proportion of females. If there are 108,000 males and 100,000 females the ratio of males to females is 1.080 and the proportion of males is 51.9%. Scientific literature often uses the proportion of males. This article uses the ratio of males to females, unless specified otherwise.