Sex ratio of the population in Japan 1955-2035

In Japan, the population sex ratio has seen only very slight changes over the past decades. In 2015, the number of men was around 95.5 for every 100 women, constituting a decrease from 96.7 in 1955.

What is the sex ratio?

The population sex ratio is determined by the sex ratio at birth, different mortality rates between men and women, as well as losses and gains through migration. In the absence of alteration, the sex ratio in human populations is quite constant, with only minor deviations. While the sex ratio at birth is usually 105 to 107, the population sex ratio, which refers to the total number of males for every 100 females, is often below 100. The reason for the shift mostly lies in differing lifestyles and physical constitutions of men and women. In general, women tend to be more resistant to disease throughout life, while men tend to engage in higher risk behavior or violence.

Influences and consequences

The sex ratio at birth and its possible determinants such as gestation environment, climate change, chemical pollution or socio-economic factors have long been subject to scientific research. Recently the impact of natural disasters, like the nuclear disaster in Japan in 2011, was presumed to influence the sex ratio at birth. The adult gender ratio has long been recognized as a key population-level determinant of behavior. However, there are many different or competing theories in existing literature about the social impacts of gender imbalance on topics such as violence, family stability, reproduction etc.