For every 100 girls born in northern India and China, more than 120 boys are born.

This staggering disparity--much higher than the naturally occurring slightly higher ratio of male births to female births--is a result of sex-selective abortions by prospective parents with a preference for male children and small families. China's one-child policy has left that country with the world's highest sex disparity--130 to 100 in some provinces, but distorted sex ratios exist in many other parts of the world, too, including Taiwan, Singapore, former communist states in the western Balkans and the Caucasus, and certain communities in the U.S.

In many of these countries, boys may be preferred for various reasons, such as the prospect of enormous dowry payments expected of a girls' parents upon her marriage, the fact that inheritance is carried through the male line, and the likelihood that a son will remain with and care for the parents in their old age, unlike daughters who would be married off. This preference, when combined with the modern desire for smaller families, produces even more skewed boy-girl ratios after the first child: parents may accept a daughter the first time around, but are more likely to abort an unborn second female child. In some places, the boy-girl ratio is 200 to 100 for a third child.

In India, gender-based abortions have been illegal since 1994. Pregnant women undergoing an ultrasound in India must sign a form agreeing not to seek to know the sex of the fetus, and doctors who disclose the sex during an examination face up to five years in prison, but the laws are hardly enforced. In China, where the number of unmarried young men may soon equal the total number of young men in America despite a ban on sex-selective abortions, the government has expressed concern "about the consequences of the large numbers of excess men for social stability and security."

The Economist has called the phenomenon "gendercide," and it is estimated that more than a 100 million sex-selective abortions have occurred to date.

Compiled from: Gendercide: Killed, Aborted, or Neglected, at Least 100 Million Girls Have Disappeared - and the Number Is Rising, The Economist (4 March 2010); Sam Roberts, U.S. Births Hint at Bias for Boys in Some Asians, The New York Times (14 June 2009); Sharon LaFraniere, Chinese Bias for Baby Boys Creates a Gap of 32 Million, The New York Times (10 April 2009); India Tries to Stop Sex-Selective Abortions, The New York Times (15 July 2007); Amelia Gentleman, Indian Prime Minister Denounces Abortion of Females, The New York Times (29 April 2008).