Hepatitis B and the Case of the Missing Women

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 some of the observed over-representation of males: the hepatitis B virus. I present new evidence, consistent with an existing scientific literature, that carriers of the hepatitis B virus have offspring sex ratios around 1.50 boys for each girl. This evidence includes both cross-country analyses and a natural experiment based on recent vaccination campagins. Hepatitis B is common in many Asian countries, especially China, where some 10 to 15 per cent of the population is infected. Using data on viral prevalence by country as well as estimates of the effect of hepatitis on sex ratio, I argue that hepatitis B can account for about 45 per cent of the "missing women": around 75 per cent in China, between 20 per cent and 50 per cent in Bangladesh, Egypt, and West Asia, and under 20 per cent in India, Pakistan and Nepal. [A revised version will be published in the Journal of Political Economy (http://www.journals.uchicago.edu/JPE/home.html), December 2005. ]