"In The Dismal Science, authors Stephen J. Dubner and Steven D. Levitt look at an argument by economist Amartya Sen that, based on ratios of men to women worldwide, there were 100 million women "missing" in Asia.

"An economics grad student at Harvard, Emily Oster, has "found" half the women by studying rates of hepatitis B, which causes pregnant women to deliver boys more often than girls.

"'Her discovery hardly means that Sen was wrong to cry misogyny, at least in some parts of the world,' the authors write. 'While Oster found, for instance, that hepatitis B can account for roughly 75 percent of the missing women in China, it can account for less than 20 percent of the boy-girl gap in Sen's native India.'"

That girls are valued far less than boys (indeed, considered disposable in various times and places) is no secret. It's just that in the 21st century you'd think we had learned to cherish all children. Guess not.