Hamamatsu Yuri, Inoue Yosuke, Watanabe Chiho, Umezaki Masahiro
Department of Human Ecology, Graduate School of Medicine,The University of Tokyo,Japan.
J Biosoc Sci. 2014 Nov;46(6):830-41. doi: 10.1017/S0021932014000017. Epub 2014 Feb 6.
On 11th March 2011 a magnitude nine earthquake struck the Tohoku region of Japan. The earthquake resulted in a large tsunami and an accident at the Fukushima Nuclear Power Plant. Previous studies have suggested that demographic indices relating to reproduction and marriage change after such massive disasters (e.g. large earthquakes). The present study investigated whether the number of births, number of marriages and the secondary sex ratio (SSR) changed after the East Japan Earthquake. The monthly number of births (males and females, separately) and marriages in each prefecture in Japan from January 1997 to June 2012 were obtained from the Demographic Survey of Japan. An analysis was performed for three different geographic boundary units: the disaster-stricken area, the non-disaster-stricken area and the whole of Japan. In each unit, the numbers of births and marriages in a given month during the post-disaster period were predicted based on a regression equation estimated by the numbers of births and marriages in that month during the pre-disaster period. The numbers of observed monthly births and marriages during the post-disaster period were compared with the predicted figures. Differences between the observed and predicted numbers were determined by referring to the 95% confidence limits for the predicted mean number. The observed probability of a male birth in a given month during the post-disaster period was compared with a 95% confidence interval of a binominal distribution. In all three boundary units, the number of births was significantly lower than the predicted number by about 3-8% from nine months after the disaster, while the number of marriages in October 2011 was significantly lower than the predicted number by about 25-28%. In October 2011, the SSR in the whole of Japan had decreased from 104.8 (the predicted SSR) to 102.9. The number of births and marriages and the SSR decreased in Japan after the East Japan Earthquake irrespective of locality.
2011年3月11日，日本东北地区发生了里氏9级地震。此次地震引发了巨大的海啸，并导致福岛核电站事故。此前的研究表明，在发生此类重大灾难（如大地震）后，与生育和婚姻相关的人口统计指标会发生变化。本研究调查了东日本大地震后出生人数、结婚人数和出生性别比（SSR）是否发生了变化。1997年1月至2012年6月期间日本各都道府县的每月出生人数（男女分开统计）和结婚人数来自日本人口动态调查。针对三个不同的地理边界单元进行了分析：受灾地区、非受灾地区和整个日本。在每个单元中，根据灾前时期该月的出生人数和结婚人数估计的回归方程，预测灾后时期给定月份的出生人数和结婚人数。将灾后时期每月观察到的出生人数和结婚人数与预测数字进行比较。观察值与预测值之间的差异通过参考预测平均数的95%置信限来确定。将灾后时期给定月份男婴出生的观察概率与二项分布的95%置信区间进行比较。在所有三个边界单元中，自灾难发生9个月后，出生人数均显著低于预测人数约3% - 8%，而2011年10月的结婚人数显著低于预测人数约25% - 28%。2011年10月，全日本的出生性别比从104.8（预测的出生性别比）降至102.9。东日本大地震后，无论地区如何，日本的出生人数、结婚人数和出生性别比均有所下降。
