(Roughly) Daily

Every time a man ejaculates, he produces somewhere between 40 million and 1.2 billion sperm. About half of those tiny swimmers carry an X chromosome and about half carry a Y. So you’d think that the odds that one or the other would be the first to fertilize an egg would be about the same as a coin flip. And yet, for as long as people have been keeping records, nature shows a different, dependable pattern: For every 100 babies born biologically female, 105 come out biologically male. Scientists have speculated this mysteriously male-biased sex ratio is evolution’s way of evening things out, since females consistently outlive their XY-counterparts—for every man that reaches the age of 100, four women have also joined the Century Club.

This biological maxim has been so drilled into the heads of demographers—the researchers responsible for keeping tabs on how many people there are on the planet—that most don’t think twice before plugging it into any projections they’re making about how populations will change in the future. But a massive effort to catalog the sex ratios at birth, for the first time, for every country, shows that’s not such a smart strategy after all.

“For so long people just took that number for granted,” says Fengqing Chao, a public health researcher at the Institute of Policy Studies in Singapore. “But no one had ever gone to the trouble of pulling all this information together to get accurate estimates of this fundamental metric.” Chao led the five-year project, combing through decades of census data, national survey responses, and birth records to build models that could estimate national sex ratios across time. In doing so, she and her collaborators at the United Nations discovered that in most regions of the world, sex ratios diverge significantly from the historical norm. Across a dozen countries, the chasm amounts to 23.1 million missing female births since 1970. The results, published in the Proceedings of the National Academy of Sciences, provide an unprecedented look at how societal values can skew the laws of nature…

The Case of the Gone Girls (and what it might mean): “First big survey of births shows millions of missing women.”

* Ben Wattenberg and Richard M. Scammon, paraphrasing Heraclitus in The Real Majority: An Extraordinary Examination of the American Electorate (Often mis-attributed to Auguste Comte– who died before the word “demography” was first cited in print.)

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As we become boosters for balance, we might send nurturing birthday greetings to Benjamin McLane Spock; he was born on this date in 1903.  The first pediatrician to study psychoanalysis to try to understand children’s needs and family dynamics, he collected his findings in a 1946 book, The Common Sense Book of Baby and Child Care, which was criticized in some academic circles as being too reliant on anecdotal evidence, and in some conservative circles for promoting (what Norman Vincent Peale and others called) “permissiveness” by parents.  Despite that push-back, it became one of the best-selling volumes in history, having sold at the time of Spock’s death in 1998 over 50 million copies in 40 languages.

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