Map of life expectancy at birth from Global Education Project.

Wednesday, July 20, 2005

I wish it were the other way around . . .

C.C. asks about a story she heard on National Pubic Radio (did I just make a typo?) regarding the sex ratio at birth in the U.S. I didn't hear the story, so I'll just have to take her word for it about the content.

The National Center for Health Statistics, which keeps track of data from birth and death certificates, among other duties, issued a report on June 14 about long-term trends in the sex ratio at birth in the U.S. (In case I haven't bored you enough already, the report is here (pdf).) For background, you need to know that, as we have known for hundreds of years actually, in humans slightly more male babies are born than female babies.* In the U.S., since about 1974, the excess of male babies has been declining, however. Not by much -- you'd hardly notice it -- but there are a helluva lot of babies born in the U.S. so even slight differences are statistically significant. Specifically, the sex ratio declined from 1.053 in 1970 to 1.048 in 2002. Not a big deal.

Biologically, the sex ratio tends to decline with the age of the mother, with the age of the father, with the number of babies the mother has had previously, with lower maternal weight, with stressors such as earthquakes and economic catastrophes, and with environmental toxins. The CDC report mentions these factors, but comes to no conclusions about the reasons for the overall decline. (Increasing average maternal age isn't enough to explain it.)

Apparently, the NPR reporter suggested that the declining sex ratio since 1974 has something to do with a higher percentage of mothers being single, and said something about tearing at the social fabric and biology punishing us for our sins or something to that effect. Evidently the reporter has some theory about unmarried women having fewer resources and therefore being under more stress, or weighing less, or some combination.

If I'm hearing this straight, it is one of the most egregious examples of reportorial malpractice I have heard of, and that's saying a lot. There is not the slightest suggestion of anything like that in the CDC analysis. The sex ratio at birth in the U.S. of 1.048 is lower than the ratio in Colombia (1.058), Egypt (1.058) El Salvador (1.063) and many other countries where presumably most married women face more material deprivation than most single women in the U.S., not to mention emotional stress from endemic violence, in the case of Colombia. Why a lower sex ratio at birth "tears at the social fabric" is unclear to me in any case. This "journalist," in the guise of reporting on an official data release, has made up a story to promote his or her personal moral crusade. Fortunately, this is a blog, so I can say stuff like that without actually knowing what I'm talking about, because again, I didn't hear the story. If anyone did, and we're being unfair, please weigh in.

UPDATE: A commenter reveals that the above representation of this story is not accurate. Still, the story seems rather dodgy to me. Please read the comments.

BTW -- the Haloscan comment counter, for reasons beyond my control (you'll have to ask Haloscan) is usually wrong. You will often see 0 comments when there are, in fact, quite a few. You may also see 3 comments when there are a dozen. So please check the comments! They're the best thing here.

*(However, men are weak and women are strong, so more male babies die, and the tendency of males to die more often, all things being equal, continues throughout the life span. That's why there are more widows than widowers. Of course, there are some societies in which girl babies are preferentially neglected or even killed, but that's another story.)

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