In another study, James has offered the hypothesis that human sex ratios, and mammalian sex ratios in general, are causally related to the hormone levels of both parents at the time of conception. The sex ratio in East Germany was also at its lowest in Female foeticide in India A map of India's child sex ratio, Social status of the mother, known to be a factor in influencing the sex ratio of certain animals such as swine,  but apparently not in humans. A scientific paper published by Jacobsen reported the sex ratio for , children born in Denmark between — According to Nicholas Kristof and Sheryl WuDunn, two Pulitzer Prize-winning reporters for the New York Times, violence against women is causing gender imbalances in many developing countries. The Indian Medical Association has undertaken efforts to prevent prenatal sex selection by giving its members Beti Bachao save the daughter badges during its meetings and conferences. Also, higher incidence of Hepatitis B virus in populations is believed to increase the male to female sex ratio, while some unexplained environmental health hazards are thought to have the opposite effect. Natural ratio[ edit ] World map of birth sex ratios, In a study around , the natural sex ratio at birth was estimated to be close to 1. According to Catalano's study, the birth sex ratio data from East Germany and West Germany over 45 years support the hypothesis. The value for the entire world population is 1. Essentially he argues that the 1: Since their independence from Soviet Union, the birth sex ratio in these Caucasus countries has risen sharply to between 1. In the warmest period over the years, the birth sex ratio peaked at about 1. Such prenatal sex determination techniques, claim Sudha and Rajan in a report, where available, favored male births. These men will remain single and will be unable to have families, in societies where marriage is regarded as virtually universal and social status and acceptance depend, in large part, on being married and creating a new family.