Hepatitis-B causes China AND Chinese-American boy/girl birth gap

[AliBabaIncorporated]

This is from a recent draft of a paper by a Harvard doctoral candidate in economics. According to her model, only 25% of the male-female gap in China --- 7.75 million individuals --- cannot be accounted for by Hepatitis-B infection, and I'd bet that most of that gap is explained by under-registration, not abortion. Of special note is the fact that there is also a sex-imbalance among births to Chinese mothers in the US (1.082 male births for every 1 female birth, as compared to the national average of 1.05:1), probably due to the same reason.

Tthe effect of maternal Hepatitis-B infection on sex-ratio at birth was noted as long as 3 decades ago in medical literature, judging by the citations in this paper. But I guess it's a lot more attractive for people --- especially parents of adopted Chinese baby girls --- to blame the gender imbalance on evil misogynistic Chinese being incentivized by capitalist reforms to kill off baby girls.

Hepatitis B and the Case of the Missing Women
Emily Oster
http://www.people.fas.harvard.edu/~eoster/hepb.pdf

Abstract
In many Asian countries the ratio of male to female population is higher than in the West --- as high as 1.07 in China and India, and even higher in Pakistan. A number of authors (most notably Sen (1992)) have suggested that this imbalance reflects excess female mortality and, as a result, have argued that as many as 100 million women are "missing." This paper proposes an explanation for much of the observed over-representation of males: the hepatitis B virus. Evidence drawn from the existing medical literature as well as new studies of recent vaccination efforts indicate that carriers of the hepatitis B virus have offspring sex ratios as high as 1.55 boys for each girl. Hepatitis B is common in many Asian countries, especially China, where some 10 to 15% of the population is infected. Using data on hepatitis B prevalence by country as well as estimates of the e®ect of hepatitis on sex ratio drawn from a wide range of sources, I find that hepatitis B can explain about 45% of the missing women: around 75% in China, between 20% and 50% in Bangladesh, Egypt, and West Asia, and less than 20% in India, Pakistan and Nepal.

[SunWuKong]

wow, i did not know the HBV causes a gender imbalance at birth.

[VV o n g B a]

some updated info on this. so... unfortunately it looks like hepatitis sex selection doesn't hold up well everywhere. and while the data is only for india, i wouldn't bet that china was different.

--------------
Abortions for sex selection in India

The Lancet has a new article (unfortunately blocked by pay wall so I'm working from the summaries) about the question of missing women in India:

Researchers based in Canada and India looked through data from a national survey, conducted among 1.1 million households in 1998, and at information about 133,738 births that took place in 1997. They found that in cases where the preceding child was a girl, the gender ratio for a second birth was just 759 girls to 1,000 boys.
And when the two previous children were girls, this ratio fell even further, to 719 girls to 1,000 boys.
On the other hand, when the preceding child or children were male, the gender ratio among successive births was about the same.
Based on the natural sex ratio in other countries, around 13.6-13.8 million girls should have been born in India in 1997 -- but the actual number was 13.1 million.

The implication, of course, is that women are using ultrasound for sex determination followed by selective abortion. This data is pretty suggestive, particularly as the effect seems to get stronger after two previous female children, which is the opposite of what you would expect if biased birth ratios were the result of some systematic bias in the women's physiology, like, say Emily Oster's hepatitis theory. The other piece of suggestive evidence is the fact that the effect is stronger from educated women, who presumably have more access to ultrasound and abortions.

http://www.educatedguesswork.org/mov...ons_for_s.html