Abstract
This study tests the evolutionary hypothesis that maternal nutritional condition can influence offspring sex ratio at birth in humans. Using the 1959–1961 Chinese Great Leap Forward famine as a natural experiment, this study combines two large-scale national data sources and difference-in-differences method to identify the effect of famine-induced acute malnutrition on sex ratio at birth. The results show a significant famine-induced decrease in the proportion of male births in the 1958, 1961, and 1964 in the urban population but not in the rural population. Given that both the urban and rural populations suffered from the famine-induced malnutrition, and that the rural population experienced a drastic famine-induced mortality increase and fertility reduction, these results suggest the presence of a short-term famine effect, a long-term famine effect, and a selection effect. The timing of the estimated famine effects suggests that famine influences sex ratio at birth by differential implantation and differential fetal loss by fetal sex.
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Notes
Despite the fact that the 1982 one-per-thousand fertility survey data is well known for its high-quality and excellent coverage and has been widely used by demographers, it is not publicly available. I gained access to the data during my tenure (2004–2009) at the Chinese Academy of Social Sciences (CASS). I obtained the data from the State Family Planning Commission (SFPC) for the CASS key research project entitled “The Past, Present, and Future Pattern of Sex Ratio at Birth in China—Some Policy Implications.” I thank both SFPC and CASS for their support of the project.
Using the 1982 fertility survey data, Song (2012) reported a significant decline in the sex ratio at birth between 1960 and 1965 and especially in 1963 and 1964. Zhao et al. (2013) verified the results using the same data. The results do not hold, however, when more recent data, the 1988 fertility survey, are used. However, the 1988 fertility survey was taken in the middle of the one-child family planning policy, which gave people much greater incentive to be “cautious” about reporting their reproductive history information than in 1982, when the policy was in its early stage.
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Song, S. Malnutrition, Sex Ratio, and Selection. Hum Nat 25, 580–595 (2014). https://doi.org/10.1007/s12110-014-9208-1
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DOI: https://doi.org/10.1007/s12110-014-9208-1