Statistically, there should be 105 females for every 100 males. However, at exactly the same time that ultrasound devices were able to determine the sex of the fetus in the womb, this statistic changed dramatically. In 1997 in China, there are now 117 male births for every 100 female births.
According to Nobel Laureate Amartya Sen – one hundred million women are missing from the world population.
Source: I am not a social activist: Making Jesus the Agenda by Ronald Sider (2008) p 103.
This article made me think of this.