Impact of the 2011 Earthquake on Marriages, Births and the Secondary Sex Ratio in Japan

Abstract

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.

Secondary Sex Ratio and Marriage After Disaster: A Reply to O'DONNELL and Behie

“…Torche & Kleinhaus (2012) showed that stress exposure, particularly in early pregnancy, was associated with a lower SSR. Our finding that the SSR was lower than the expected range at 7 months after the 2011 earthquake (Hamamatsu et al, 2014) was consistent with previous studies. It suggests that experiencing an earthquake in months two or three of gestation may result in a significant decline in the SSR.…”

“…O'Donnell & Behie (2014) noted the possibility of a small increase in marriage rates in 2012 in some disaster-stricken prefectures. To confirm their observation, we evaluated the total number of marriages in 2012 (10-21 months after the 2011 earthquake) in four different geographical areas: the whole of Japan, the disaster-stricken area, the non-disaster-stricken area and each prefecture (n ¼ 47), and performed a quadratic regression analysis, which was also used in Hamamatsu et al (2014). Table 1 shows that the total number of marriages recorded in 2012 fell within the range of the 95% confidence limits (CL) for the predicted mean number of marriages in the whole of Japan, the disaster-stricken area and the non-disaster-stricken area.…”

Association of the Great East Japan Earthquake and the Daiichi Nuclear Disaster in Fukushima City, Japan, With Birth Rates

“…The decreased number of births from December 2011 to June 2012 in the 13 prefectures affected by the Great East Japan Earthquake and the FDNPP disaster (including Fukushima prefecture) was reported by a previous study. 3 However, as its authors acknowledged clearly, only a short period (7 months) was examined. In contrast, the present study examined a period of 11 years and identified long-term trends in birth rates using an interrupted time series design.…”

“…One previous study showed that the number of births decreased in the 13 prefectures affected by the Great East Japan Earthquake and the FDNPP disaster (including Fukushima prefecture) between December 2011 and June 2012. 3 On the other hand, mass media reported that, while there was a slight recovery in the number of births in Fukushima Prefecture 2 years after the disaster (in 2013), the numbers decreased again in 2016 based on vital statistics in the prefecture. 4 , 5 However, whether or how the trend in birth rates in the Fukushima Prefecture changed after the disaster has not been examined thoroughly in the extant literature.…”

Factors Associated With Intention of Future Pregnancy Among Women Affected by the Fukushima Nuclear Accident: Analysis of Fukushima Health Management Survey Data From 2012 to 2014

“…A previous study found that the number of births declined in Japan after the 2011 disaster at the national level (ie, irrespective of proximity to the affected area). 3 Given the strong interest in increasing the birth rate in Japan and in other developed countries, and the fact that any country with nuclear power plants can potentially be affected by a nuclear accident like Japan, it is critically important to understand how a nuclear accident and radiation contamination affect women’s perceptions and decisions about future pregnancy.…”