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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.


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Asian Development Bank (2012) Addressing Climate Change and Migration in Asia and the Pacific. Asian Development Bank, Mandaluyong City.
Bongaarts, J. (2001) Fertility and reproductive preferences in post-transitional societies. Population and Development Review 27 (supplement), 260281.
Bowlby, J. (1969) Attachment and Loss, Volume I: Attachment. Basic Books, New York.
Cabinet Office, Government of Japan (2012) The Economic Condition in Japan 2011–2012 [in Japanese]. URL:
Catalano, R., Bruckner, T., Gould, J., Eskenazi, B. & Anderson, E. (2005) Sex ratios in California following the terrorist attacks of September 11, 2001. Human Reproduction 20(5), 12211227.
Cohan, C. L. & Cole, S. W. (2002) Life course transitions and natural disaster: marriage, birth, and divorce following hurricane Hugo. Journal of Family Psychology 16, 1425.
Davis, D. L., Webster, P., Stainthorpe, H., Chilton, J., Jones, L. & Doi, R. (2007) Declines in sex ratio at birth and fetal deaths in Japan, and in U.S. whites but not African Americans. Environmental Health Perspective 115, 941946.
Finlay, J. (2009) Fertility response to natural disasters: the case of three high mortality earthquakes. World Bank Policy Research Working Paper Series 4883. The World Bank, Washington, DC.
Fukuda, M., Fukuda, K., Shimizu, T. & Møller, H. (1998) Decline in sex ratio at birth after Kobe earthquake. Human Reproduction 13, 23212322.
Hansen, D., Møller, H. & Olsen, J. (1999) Severe periconceptional life events and the sex ratio in offspring: follow up study based on five national registers. British Medical Journal 319, 548549.
Iwasawa, M., Kamata, K., Beppu, M. & Mita, F. (2012) The prediction of fertility considering the effect of the earthquake. In Ishii, F. (ed.) Incorporation of Foreign-Born Population and its Impact on Future Population Dynamics and Social Security in Japan [in Japanese]. Report of the fiscal year 2011 for Health Labour Sciences Research Grant, pp. 233246.
Japan Meteorological Agency (n.d.) The 2011 Earthquake off the Pacific Coast of Tohoku. URL:
Kotozaki, Y. & Kawashima, R. (2012) Effects of the Higashi-Nihon earthquake: posttraumatic stress, psychological changes, and cortisol levels of survivors. PloS One 7(4), e34612.
Lyster, W. (1974) Altered sex ratio after the London smog of 1952 and the Brisbane flood of 1965. Journal of Obstetrics and Gynaecology of the British Commonwealth 81, 626631.
McLeod, J. D. (1994) Anxiety disorders and marital quality. Journal of Abnormal Psychology 103, 767.
Matsuda, S. & Kahyo, H. (1994) Geographical differences and time trends in the seasonality of birth in Japan. International Journal of Epidemiology 23, 107118.
Miura, T. (1987) The influence of seasonal atmospheric factors on human reproduction. Experientia 43, 4854.
Mizuno, R. (2000) The male/female ratio of foetal deaths and births in Japan. The Lancet 356(9231), 738739.
National Police Agency of Japan (n.d.) Damage Situation and Police Countermeasures Associated with 2011 Tohoku District – off the Pacific Ocean Earthquake. URL:
Okada, N., Ye, T., Kajitani, Y., Shi, P. & Tatano, H. (2011) The 2011 eastern Japan great earthquake disaster: overview and comments. International Journal of Disaster Risk Science 2(1), 3442.
Prime Minister of Japan and His Cabinet (n.d.) Great East Japan Earthquake: Health and Safety. URL:
Retherford, R. D., Ogawa, N. & Sakamoto, S. (1996) Values and fertility change in Japan. Population Studies 50, 525.
Ruther, M. (2010) The Fertility Response to September 11th: Evidence from the Five Boroughs. Population Studies Centre, University of Pennsylvania, Philadelphia.
Statistic Bureau of Japan (n.d.) E-Stat: Portal Site of Official Statistics of Japan. URL:
Takagi, K. (2011) Abnormality and accidental diseases of pregnant women. In Aoki, Y., Hirasawa, M. & Kato, N. (eds) The System of Midwifery 3: Pathologic Physiology of Pregnancy and Delivery [in Japanese]. Nihon Kango Kyokai Press, Tokyo, pp. 4376.
Takahashi, M. & Nagai, M. (2008) The seasonality of sex ratio [in Japanese]. Japan Journal of Hygiene 63(2), 461.
Torche, F. & Kleinhaus, K. (2012) Prenatal stress, gestational age and secondary sex ratio: the sex-specific effects of exposure to a natural disaster in early pregnancy. Human Reproduction 27, 558567.
Udry, J. R. (1970) The effect of the great blackout of 1965 on births in New York City. Demography 7(3), 325327.
White, L. & Rogers, S.J. (2004) Economic circumstances and family outcomes: a review of the 1990s. Journal of Marriage and Family 62, 10351051.
Yamada, M. (2007) Declining Birth Rate in Japan: Another Gap [in Japanese]. Iwanami Press, Tokyo.
Zorn, B., Šučur, V., Stare, J. & Meden-Vrtovec, H. (2002) Decline in sex ratio at birth after 10-day war in Slovenia: brief communication. Human Reproduction 17, 31733177.




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