Estimating the Effect of the One-Child Policy on the Sex Ratio Imbalance in China: Identification Based on the Difference-in-Differences

Abstract

In China, the male-biased sex ratio has increased significantly. Because the one-child policy applies only to the Han Chinese but not to minorities, this unique affirmative policy allows us to identify the causal effect of the one-child policy on the increase in sex ratios by using a difference-in-differences (DD) estimator. Using the 1990 census, we find that the strict enforcement of the one-child policy led to 4.4 extra boys per 100 girls in the 1980s, accounting for about 94% of the total increase in sex ratios during this period. The robust tests indicate that the estimated policy effect is not likely confounded by other omitted policy shocks or socioeconomic changes. Moreover, we conduct the DD estimation using both the 2000 census and the 2005 mini-census. Our estimates suggest that the one-child policy resulted in about 7.0 extra boys per 100 girls for the 1991–2005 birth cohorts. The effect of the one-child policy accounts for about 57% and 54% of the total increases in sex ratios for the 1991–2000 and 2001–2005 birth cohorts, respectively.

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Fig. 1
Fig. 2

Notes

  1. 1.

    The sex ratio is defined as the number of males per 100 females in the reference population.

  2. 2.

    It has also been suggested that the endogenized sex ratio by the son preference may systematically degenerate girls to be born in low-status families (Edlund 1999).

  3. 3.

    The interaction between sex preference, fertility, and sex ratio has long been recognized in the literature (Becker 1991; Ben-Porath and Welch 1976).

  4. 4.

    Second births were strictly forbidden at the early stage of the implementation of the one-child policy after 1979. However, Central Document 7, issued in early 1984 by the Party Central Committee, allows rural couples to have a second child if the first was a girl (Peng 1996).

  5. 5.

    Two facts greatly substantiate the validity of our quasi-experimental design of the DD estimator. First, there is clear evidence that the sex ratios for minorities and the Han were very close prior to the enactment of the one-child policy but diverged significantly afterward. Second, there is little difference between Han and minorities in changes of family structure, mother’s age at first birth, parental characteristics, and parental labor market behaviors during the post-treatment period. Li and Zhang (2009) constructed a similar DD estimator based on the differential treatment across ethnic groups to test the external effects of fertility behavior. Li and Zhang (2007) also exploited the differential treatments of the one-child policy between the Han and minorities to construct an instrumental variable to identify the effect of (endogenous) population growth on economic growth.

  6. 6.

    The four modern population censuses used in Coale and Banister (1994) were conducted in 1953, 1964, 1982, and 1990, and the two in-depth fertility surveys were carried out in 1982 and 1988.

  7. 7.

    This figure is very similar to Coale and Banister’s (1994) Figure 2 except that their cohort analysis was conducted in a five-year moving average form to smooth out irregular disturbances.

  8. 8.

    Descriptive statistics from various sources show that the ratio of female wages to male wages hovered around 80% throughout the 1980s and 1990s, which is comparable to that in the United States during the same period (Blau and Kahn 1997; Gustafsson and Li 2000; Meng 1998).

  9. 9.

    Since the dependent variable is a dummy variable, a logit model would seem to be a natural choice. However, a linear probability model facilitates the interpretation of our DD estimates, as shown above. The major results in our article are confirmed when we use a logit model.

  10. 10.

    Besley and Case (2000) addressed the endogeneity in the implementation of policies in natural experiment studies.

  11. 11.

    The reason that the birth year is truncated at 1972 is that children born in 1973 were just 17 years old in the census year of 1990. Since 18 is the legal minimum age for full-time work in China, most children younger than 18 are still economically dependent on and living with their parents.

  12. 12.

    Because the census contains no information about children no longer living at home, excluding those households with children living outside home will result in a biased sample. Following Angrist and Evans (1998), we restrict mother’s age to less than or equal to 38 to mitigate the sample-selection problem. Because the minimum age for marriage as prescribed by the Chinese Marriage Law is 20, the age cutoff is 17 for the eldest children of these women, and most of these children are still living with their parents.

  13. 13.

    The difference in sex ratios between the Han and minorities in the post–policy change period is given by \( 100 \times {\left[ {0.5234/{\left( {1 - 0.5234} \right)} - 0.5124/{\left( {1 - 0.5124} \right)}} \right]} \), which equals 4.7 (note that 0.5234 and 0.5124 are from the last row of columns 1 and 2 in Table 2).

  14. 14.

    We conducted the DD estimation on the rural and urban subsamples, respectively, and found that the DD estimates were statistically significant only for the rural subsamples. For a detailed discussion, see Li et al. (2010).

  15. 15.

    We also analyzed the time pattern of the DD estimates by birth year (Li et al. 2010). We found that the time pattern of our DD estimates is highly consistent with the implementation stages of the one-child policy in the 1980s.

  16. 16.

    The 1.5-child policy refers to the policy that allows rural families with a first-birth girl to have a second birth.

  17. 17.

    Guo (2005) and Gu et al. (2008) analyzed fertility rates and sex ratios across different policy regimes. It would be interesting to explore the causal effects of the 1-, 1.5-, and 2-child policies on sex ratios among the Han Chinese. However, these policies among the Han Chinese are suspected to be endogenously imposed. In contrast, the differential treatment of the policy across ethnic groups is evidently exogenously imposed.

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Acknowledgments

The work described in this article was substantially supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. CUHK 454608). We thank the editors and two anonymous referees for valuable comments.

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Correspondence to Junsen Zhang.

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Li, H., Yi, J. & Zhang, J. Estimating the Effect of the One-Child Policy on the Sex Ratio Imbalance in China: Identification Based on the Difference-in-Differences. Demography 48, 1535–1557 (2011). https://doi.org/10.1007/s13524-011-0055-y

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Keywords

  • One-child policy
  • Sex ratio imbalance
  • Difference-in-differences estimator