"Abortion and sex selection in the United States":

Two days ago, economists Douglas Almond and Lena Edlund published an article in Proceedings of the National Academy of Sciences examining the ratio of male to female births in "U.S.-born children of Chinese, Korean, and Asian Indian parents." Among whites, the boy-girl ratio was essentially constant, regardless of the number of kids in a family or how many of them were girls. In the Asian-American sample, the boy-girl ratio started out at the same norm: 1.05 to 1. But among families whose first child was a girl, the boy-girl ratio among second kids went up to 1.17 to 1. And if the first two kids were girls, the boy-girl ratio among third kids went up to 1.5 to 1. This 50 percent increase in male probability is directly contrary to the trend among whites, who tend to produce a child of the same sex as the previous child.

There's no plausible innocent explanation for this enormous and directionally abnormal shift in probability. The authors conclude that the numbers are "evidence of sex selection, most likely at the prenatal stage."

Sex selection of this magnitude has previously been documented in China, South Korea, and India, but not in the U.S.