The 1918 influenza pandemic and subsequent birth deficit in Japan

(ProQuest: . denotes formulae omitted.)1. IntroductionThe 1918 influenza pandemic, variously known as the "mother of all pandemics" (Taubenberger and Morens 2006) for its impact on global population and the "forgotten pandemic" (Crosby 2003) for the relative lack of attention researchers have paid to it, is one of the "big three" pandemics in recorded history (Langford 2002; Patterson 1983). Demographic research on the subject has focused heavily on patterns of mortality, paying relatively little attention to the equally important phenomenon of fertility. What little research there is on the impact of the 1918 influenza on human fertility has found a link between excess mortality during the pandemic period and subsequent changes in births and birth rates. For example, Mamelund's research on Norway observed a dip followed by a baby boom (Mamelund 2004), while Bloom-Feshbach and colleagues (Bloom-Feshbach et al. 2011) found a birth deficit 6-7 months after pandemic-associated deaths peaked in Scandinavia and the USA. Mamelund (2004, 2012) argues for social as well as behavioral mechanisms as drivers of pandemic-associated changes in fertility. By contrast, Bloom-Feshbach et al. emphasize biological mechanisms and embryonic loss in the late stage of the first trimester as contributors to subsequent birth declines.This study utilizes data from Japan to determine whether there is a link between pandemic-associated excess mortality and later births, to evaluate the length of the time-lag between changes in excess mortality and future births, and to explore the mechanisms (i.e., socio-behavioral, biological, or both) at play in this link. This study makes two contributions to the literature. First, the statistical analysis reveals a nine-month lag between pandemic-associated excess mortality and subsequent birth declines. Second, our findings from the Japanese dataset augment a growing body of literature on the 1918 influenza pandemic, which has traditionally been centered on the Western experience but is now expanding to encompass the experiences of non-western countries.The 1918 influenza pandemic claimed more than 50 million lives around the world (Johnson and Mueller 2002). Japan and several other major population centers in Asia, including India and Indonesia, were not spared the ravages of the pandemic (Chandra 2013a, 2013b; Chandra, Kuljanin, and Wray 2012). Earlier research indicated that Japan experienced a low death rate of between 0.64% and 0.71% (calculations based on Patterson and Pyle 1991 and Johnson and Mueller 2002) during the pandemic compared to most European countries and all known Asian death counts. However, a recent study argued that the total pandemic-associated population loss of 1.97-2.2 million, which includes excess deaths and reduced births, demonstrating that the Japanese experience was similar to those of other countries (Chandra 2013a). The pandemic also caused an excess of stillbirths in Japan (Nishiura 2009). In a pattern similar to that of its colony, Taiwan (Chandra and Yu, 2015), Japan experienced two major waves of mortality during the pandemic, the first between October 1918 and February 1919 with a peak in November 1918, and the second between October 1919 and February 1920 with a peak in January 1920 (Ding 2008; Richard et al. 2009). According to official reports from the Japanese Sanitary Bureau, a total of over 19.2 million infected cases were reported during the first outbreak, resulting in over 204,000 deaths and a death rate of approximately 1.06% (Central Sanitary Bureau 1920). During the second wave, in January 1920 alone there were 1,333,000 infected cases and 55,000 deaths (Central Sanitary Bureau 1920). Although the influenza virus entered Japan through seaports and the pandemic first broke out in coastal cities, the remoteness of rural areas did not protect them (Central Sanitary Bureau 1920; Nishiura and Chowell 2008; Rice 2003). 2. Data and methodsThe data for this study included monthly figures on deaths, births, and stillbirths from 1913 to 1925 from the Annual Report of the Central Sanitary Bureau of the Department for Home Affairs of the Imperial Japanese Government (Central Sanitary Bureau 1920). …