technology that greatly facilitated sex-selection, resulting in sharp rises in child sex ratios from the 1980s. The South Korean data offer an interesting insight into this process: while the _manifestation_ of son preference rose with the advent of the new technology, the reported _intensity_ of son preference was falling (Chung and Das Gupta 2007). Between 1985 and 1994 the percentage of women reporting strong son preference nearly halved, but the sex ratio at birth rose. After that, the effect of reduced son preference prevailed, and the sex ratio at birth dropped sharply in South Korea.

South Korea is a small and homogenous country compared with China and India’s enormous size and heterogeneity, but similar processes seem to be at work in many regions of China and India. Retherford and Roy’s (2003: 72) analysis of trends in ideal sex ratios in India during the 1990s concluded that “son preference is declining in almost all states and in almost all socio-economic groups within states”. Their analysis was based on the first two NFHS surveys, and the third survey recently released shows that son preference continues to decline steadily ― including in Punjab and Haryana, the states that have consistently shown the highest child sex ratios in the country (Table 2). China’s quinquennial censuses make it easier to detect recent trends in child sex ratios than in India, which only holds decennial censuses. The Chinese census data indicate that many of the provinces in the East and Central South regions ─ which have historically had the highest child sex ratios ─ show a fall in these ratios in recent years (Das Gupta et al 2009). Guilmoto (2009) also anticipates a progressive decline in sex selection in these areas.

# **4.  CONCLUSIONS**

Kinship systems matter ― the more kinship rules exclude adult daughters from contributing to their parents, the lower the incentives for parents to raise girls. Girls and boys are equally likely to help their parents in bilateral and matrilineal kinship systems. Patrilineal systems vary in the extent to which they allow some flexibility for adult daughters to remain close to their parents, and these differences in kinship rules are reflected in differences in sex ratios.

The correspondence between kinship rules and son preference is striking. Within the same country, different levels of permissible contact between daughters and their parents (as documented in ethnographic studies) are mirrored in regional differences in child sex ratios in India, and in regional and ethnic differentials in China. Even within the same culture, variations in kinship system matter ― in South Korea, the eldest son is primarily responsible for continuing the family line, and this is reflected in stronger son preference than that expressed by the wives of other sons.

But what explains the fact that China, South Korea and Northwest India manifest such extreme son preference compared with other patrilineal societies? Why are they organized into such tight units defined through the male line alone, leaving so little flexibility for women to play a part in their household of birth ─ and (for example) cannot inherit parental property even if they have no brothers? This paper argues that what makes these societies unique is that their premodern political and administrative systems used patrilineages to organize and administer their citizens. The interplay of culture, state, and political processes shaped gender roles and the relative value of boys and girls to their parents, underpinning a rigidly patrilineal kinship system.

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