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Numerological preferences, timing of births and the long-term effect on schooling


Cultural beliefs may affect demographic behaviors. According to traditional Chinese astrology, babies born on auspicious days will have good luck in their lifetime, whereas those born on inauspicious days will have bad luck. Using administrative data from birth certificates in Guangdong, China, we provide empirical evidence on the short-term effects of such numerological preferences. We find that approximately 3.9% extra births occur on auspicious days and 1.4% of births are avoided on inauspicious days. Additionally, there is a higher male/female sex ratio for births on auspicious days. Since such manipulation of the birthdate is typically performed through scheduled C-sections, C-section births increase significantly on auspicious days. Moreover, we use a second dataset to examine the long-term effect of numerological preferences and find that people born on auspicious days are more likely to attend college.

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  1. The Chinese zodiac (Shengxiao) is based on the lunar calendar, in which each year is symbolized by a zodiacal sign that follows a 12-year mathematical cycle of 12 animals, namely the Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Pig.

  2. Although many studies analyze the determinants of the C-section, most of them focus on the financial incentives or demand for leisure by physicians. For example, Brown (1996) indicates that time-dependent dummy variables related to leisure are significant predictors of both total and unplanned C-sections. On the basis of a survey data from three hospitals in Greece, Mossialos et al. (2005) find health insurance, socio-economic status (proxied by ethnic background), and physician convenience increase the occurrence of C-sections. In a recent study, Long et al. (2012) investigate the association between the use of C-sections and insurance coverage by the New Co-operative Medical Scheme in rural China. They document that health insurance facilitates the overuse of non-emergency C-section.

  3. More than 99% of births in Guangdong Province take place in hospitals.

  4. APGAR is the abbreviation of Activity, Pulse, Grimace, Appearance, and Respiration, which is tested immediately (e.g., 1 min) after delivery to assess neonatal health. Each item is scored from 0 to 2; thus, a total score is 10. In general, a total score between 7 and 10 is considered normal.

  5. Although modern China has adopted the solar calendar, the lunar calendar is still used for traditional festivals and cosmology and astrology. In general, the lunar calendar lags 3 to 6 weeks behind the Western solar calendar (Lin et al. 2006).

  6. To reduce the computational burden, we take the day level as the unit of observation but use the number of observations as a weight. Estimation at the mean of each birthdate produces the same results as the individual level.

  7. Some studies have demonstrated that numerological preferences relate to many aspects of life for Chinese people. For example, Brown and Mitchell (2008) detected that the prices of A-shares (mainly held by Chinese individuals) traded on the Shanghai stock exchange were more than twice as likely to end in 8 than 4. Fortin et al. (2014) found that in a North American market with many Chinese residents, houses with an address number ending in four sold for a price 2.2% lower and those ending in 8 sold for a price 2.5% higher compared with other houses.

  8. They also find a large geographic variation in C-section rates: Tibet had the lowest at 4%, Jilin the highest at 62.5%, and Guangdong Province was in the middle at 25.9% in 2014. The time trend is steady in Guangdong, with 23.2%, 24.1%, 25.4%, 25.2%, 25.9%, and 26.4% from 2008 to 2013. Our birth certificates contain information on delivery type only in 2015 and 2016. The rates are 27.2% and 26.5%, respectively, very close to the rate calculated for 2014.

  9. Both birth weight and Apgar scores are often used as important proxy variables for initial health at birth in the literature, especially for birth weight, which is associated with various child outcomes (see, for example, Black et al. 2007; Figlio et al. 2014).

  10. All the specifications in this analysis use linear probability model where the dependent variable is a binary indicator. Our results are also robust to if we estimate with a probit model.

  11. Note that variables indicating birthdates containing the number four or eight are not included in the regression because (1) we do not find any significant response to number 4 on the birth timing results mentioned above and (2) adding these variables will further decrease the degrees of freedom, given the relatively small sample size (N = 134) in this analysis. Our findings are robustness to alternative specifications, i.e., the number variables are included progressively in Eq. (2).

  12. We also include Jiangxi, Guangxi, and Hainan Provinces that abut Guangdong but have different cultural beliefs. However, all the results are statistically insignificant. Because Guangdong is regarded as one of the areas most noted for belief in Chinese traditional culture, the numerological preferences may be more prevalent among people of Guangdong (the short-term results also support this predication). Consequently, the findings regarding birth manipulations are not necessarily applicable nationwide.


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We thank the Family Planning Research Institute of Guangdong Province for generously providing the data for this paper. We also thank the anonymous referees of the Journal of Population Economics for their comments and guidance. All errors are ours.

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Correspondence to Shiying Zhang.

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Appendix. An example of auspicious days and inauspicious days

Appendix. An example of auspicious days and inauspicious days

Auspicious days: September 2014

figure a

Inauspicious days: September 2014

figure b

Auspicious days (in red) and inauspicious days (in gray) in 2014

figure c

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Table 12 Test the birth timing mechanism

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Huang, C., Ma, X., Zhang, S. et al. Numerological preferences, timing of births and the long-term effect on schooling. J Popul Econ 33, 531–554 (2020).

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  • Numerological preferences
  • Birthdate
  • Timed births
  • Chinese astrology


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  • Z10
  • J13
  • D19