Suchergebnisse

SummaryThe secondary sex ratio (SSR) has been suggested to decrease with adverse physical and psychological environments. Previous studies have focused on reduced SSR under adverse conditions, such as war, terrorism attack and earthquake, but few studies have investigated fluctuations in SSR in moderately adverse environments. This study analysed municipality-level vital statistics records in Japan collected between 1998 and 2002 to identify high-SSR clusters and low-SSR clusters with spatial-scan statistics. In 999 runs of simulation, high- and low-SSR clusters were detected but fewer than 950 times, indicating that SSR was not geographically clustered in Japan if type I error of 5% was adopted. Explorative analyses comparing demographic attributes between high-SSR clusters and low-SSR clusters that were detected more than 500 times in 999 runs of simulation, showed that rate of spontaneous abortion, rate of artificial abortion and divorce rate were higher in low-SSR clusters, while male life expectancy, female life expectancy and total fertility rate were higher in a high-SSR cluster.

SummaryOn 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.