HBV status, the data from Livadas et al’s (1979) study would be inconsistent with Oster’s reformulated hypothesis.

Her second approach uses population-level data from Taiwan (China). Using data on HBV prevalence by age from testing done in primary school, she constructs expected HBV prevalence by 5-year age cohort. She then examines the sex ratio of children born to parents who belong to different age cohorts, so their probability of infection differs. Once again, she finds that only the expected HBV of the father’s cohort affects the sex ratio at birth. It is difficult to assess this information since she does not present basic information on the data, such as the number of agecohorts available for this analysis. 9 Her third approach uses United States census data to look for patterns in the sex ratios of children born to Chinese immigrants, who are assumed to have levels of HBV prevalence similar to their place of origin. She finds that Chinese couples have an elevated sex ratio, as do Chinese men who marry non-Chinese. However, Chinese women who marry non-Chinese do not show an elevated sex ratio at birth. She interprets this as showing that only paternal HBV status drives the elevated sex ratio at birth. However, there could be a completely different explanation for this. The literature on son preference in China highlights the fact that people want sons in order to continue the _husband_ ’s lineage — not that of the wife, since a woman cannot continue her own lineage. Even if married to an American-born woman, a Chinese-born man would still be subject to pressure to continue his lineage, but this would not apply to a Chinese-born woman married to an American-born man.

There are thus several questions that arise about Oster’s evidence that it is the father’s and not the mother’s HBV status that causes the elevated sex ratios at birth. In any case, the demographic evidence below indicate that hepatitis B (whether of the father or the mother) cannot account, as Oster has argued, for the bulk of the female deficit in China.

# **II    The Demographic Evidence**

# **_1.  Whether a girl goes “missing” in China depends heavily on whether she has older sisters_**

A very clear pattern emerges from the third of a million births in the one percent sample of the 1990 Chinese census. Note that this pertains to births during 1989-90, which is close in time to that for which Oster made her calculations on the proportion of the female deficit in China attributable to HBV (Oster 2005, Table 11). This enormous database of births shows that the **_<u>only</u>_** group of women with elevated probabilities of bearing a son is those who have already borne daughters (Figure 1). Those who have borne only son(s) show a mildly elevated probability of the next child being a _girl_ — indicative of a mild preference for having a daughter if the sons are already safely in place.

A study of the sex ratio of aborted fetuses in China (Gu and Roy 1995, see Table 2) shows a pattern entirely consistent with that of the sex ratio of births — namely, that women who have only daughters account for the bulk of the excess of female fetuses among the total abortions. A similar pattern of son preference is found across Asia, showing that parental discrimination against girls is related to the sex composition of their children. Studies in India, Bangladesh, and South Korea,<sup>10</sup> based on data from before the availability of sex-selection technology (when households resorted to infanticide or discrimination during early childhood), show that girls born 4