# Far-reaching effects of bombing on fertility in mid-20th century Japan

Tatsuki Inoue, Erika Igarashi School of Commerce, Meiji University, Faculty
Office Building, 1-1, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8301, Japan
(E-mail: tatsukiinoue@meiji.ac.jp).Institute for Advanced Study, Hitotsubashi
University, 708, Faculty Building 2, 2-1, Naka, Kunitachi, Tokyo, 186-8601,
Japan (E-mail: igarashi.erika715@r.hit-u.ac.jp).

###### Abstract

This study explores the indirect impact of war damage on postwar fertility,
with a specific focus on Japan’s air raids during World War II. Using 1935 and
1947 Kinki region town/village data and city air raid damage information, we
explored the “far-reaching effects” on fertility rates in nearby undamaged
areas. Our fixed-effects model estimates show that air raids influenced
postwar fertility within a 15-kilometer radius of the bombed cities. These
impacts varied based on bombing intensity, showing both positive and negative
effects. Moreover, a deeper analysis, using the Allied flight path as a
natural experiment, indicates that air raid threats and associated fear led to
increased postwar fertility, even in undamaged areas. This study highlights
the relatively unexplored indirect consequences of war on fertility rates in
neighboring regions and significantly contributes to the literature on the
relationship between wars and fertility.

Keywords: Air raids, Bombing; Fear; Fertility; World War II

JEL Codes: J13; N35; N45

##  1 Introduction

Despite international peacekeeping efforts, wars and conflicts persist. In
2020, there were 56 active conflicts worldwide (Strand and Hegre 2021). More
recently, the military crash between Russia and Ukraine in 2022 attracted
global attention. Given the current situation, it is increasingly essential to
gain multifaceted foresight into postwar societies and to deepen our
understanding of war.111The most recent economic research delving into postwar
changes includes Boehnke and Gay (2022); Padilla-Romo and Peluffo (2023);
Koenig (2023); Akresh et al. (2023); Bose et al. (2022); Korovkin and Makarin
(2023); Prem and Vargas (2023); Beaman et al. (2022); Vlachos (2022). In
addition, the origins of and preventive measures against wars and conflicts
have been examined (Narciso and Severgnini 2023; Gallea 2023; Mueller and Rauh
2022; Castells-Quintana et al. 2022; Rexer 2022; Mayoral and Ray 2022). As
seen in the mid-twentieth century baby boom, postwar fertility rate changes
can profoundly impact society. This study investigates the effects of war
damage on postwar fertility from a new perspective by utilizing Japan’s
experience with air raids during World War II. We examine the far-reaching
effects, which are the indirect effects of war damage on the fertility rate,
in undamaged areas near war-damaged ones.

Japan offers an ideal setting for examining far-reaching effects. Despite
intensified air raids on cities in early 1945, towns and villages mostly
escaped direct damage, as the Allied Forces focused solely on bombing cities.
Furthermore, city damage varied significantly, with the Kinki region having
both war-damaged and non-damaged cities.222The Kinki region is located roughly
in the center (slightly to the west) of Japan (see Online Appendix A). This
study treats Mie, Shiga, Kyoto, Osaka, Hyogo, Nara, and Wakayama Prefectures
as the Kinki region according to the general classification. When controlling
for relevant variables, city bombing damage is considered independent of
fertility determinants in the surrounding rural areas. Thus, we capture the
far-reaching effects by focusing on fertility changes in towns and villages
near bombed cities. Japan’s experience provides further helpful situations.
Allied aggression primarily involved aerial bombing, given Japan’s geography.
These cities were devastated by intense air raids over a relatively brief
period. Furthermore, the Japanese government’s covert information controls
effectively limited the spread of the bombing’s indirect effects.

Our dataset includes town- and village-level crude birth rates, a well-
established measure of fertility in the historical context, in the Kinki
region in 1935 and 1947, along with air raid damage information for cities
during WWII. To eliminate the impact of direct damage and to focus on far-
reaching effects, we excluded cities from our observations. Comprehensive
regional-level data helped resolve the potential issue of sample selection
bias. The data sources for this study are population censuses and the most
reliable reports of air raid damage surveyed by the Economic Stabilization
Board. As an identification strategy, this study employs a fixed-effects model
with the essence of a difference-in-differences approach, using the death toll
from bombings in nearby cities as the treatment to represent the scale of the
air raids. Consequently, our estimates avoid the influence of war-related
macro shocks and time-constant characteristics.

To identify some of the mechanisms behind the far-reaching effects, this study
leverages the Allied flight path to Japan as a natural experiment. The bombers
of the Allied Forces only flew from the Mariana Islands, located southeast of
Japan, due to flight distance limitations. Consequently, southeastern towns
and villages in bombed cities were exposed to stronger fear, a potential
factor, than those in other directions. However, other potential mechanisms
are independent of the orientation of the cities. Therefore, we can capture
far-reaching effects through fear by investigating the differences in the
effects between the southeast and other directions.

The estimation results suggest that air raids during WWII affected the postwar
fertility rate in towns and villages within at least 15 km. While large-scale
air raids positively affected postwar fertility rates, small-scale air raids
had a negative impact. A back-of-the-envelope calculation indicates that
aerial bombings increased the crude birth rate by 3.90% in severely damaged
cases and decreased it by 4.74% in other cases. Moreover, the quasi-
experimental approach demonstrates that the far-reaching effects of bombings
are negative in municipalities located non-southeast of the nearest bombed
city but are more positive in the southeast, especially in the severely
damaged group. These results suggest that the intense fear caused by air raids
led to postwar increases in the fertility rate, while the negative effects
were likely attributable to other factors, such as the enhancement of national
morale.

The contributions of this study are as follows: We discovered that air raids
influenced postwar fertility, even in nearby areas that were not directly
damaged. While numerous studies have examined war’s impact on fertility,
focusing on macro and direct effects, our research explores the indirect
effects on neighboring regions.333As for macro shocks, there is literature on
the mobilization and demobilization (Van Bavel and Reher 2013), absence of men
during wartime (Woldemicael 2008), scarcity of men in the postwar period
(Brainerd 2017; Bethmann and Kvasnicka 2012; Kraehnert et al. 2019; Jayaraman
et al. 2009; Kesternich et al. 2020), gender imbalance in the marriage market
(Ogasawara and Komura 2022), changes in the demand for female labor (Doepke et
al. 2015; Brodeur and Kattan 2022), high relative income (Easterlin 1961; Hill
2015), decline in educational level (Islam et al. 2016; Urdal and Che 2013),
economic difficulty and health deterioration (Lindstrom and Berhanu 1999;
Kidane 1989; Sobotka et al. 2011), and political instability (Williams et al.
2012). These shocks have broad impacts on participating countries or regions
but are independent of individual-level war damage from direct attacks.
Studies on individual shocks examine child death (Kraehnert et al. 2019;
Heuveline and Poch 2007), sibling death (Kraehnert et al. 2019), an increase
in child mortality risk (Verwimp and Van Bavel 2005; Lindstrom and Berhanu
1999), and the threat of harm (Williams et al. 2012). However, the indirect
effects of war damage on fertility rates in neighboring areas remain
understudied. Agadjanian and Prata (2002) found a remarkable postwar rebound
in fertility in the capital city of Angola, despite the minimal direct impact
of the war, in response to the politico-military and economic changes.
However, this impact differs from the far-reaching effects we have focused on,
which depend on distance and damage extent near affected areas. Thus, this
study adds a novel perspective to previous research on postwar birth rate
changes. Additionally, our findings imply that comparisons between damaged and
non-damaged areas nearby may overestimate or underestimate the war’s impact.

Moreover, this study presents new evidence contributing to the literature on
short-term fertility changes in response to destructive shocks, such as
natural disasters and terrorism (for example, Rodgers et al. 2005; Nobles et
al. 2015; Cohan and Cole 2002; Frankenberg et al. 2014; Kidane 1989; Nandi et
al. 2018). These previous studies have examined the impact of shocks and
potential channels. We have discussed how air raids could influence postwar
birth rate in areas outside the bombed zones and have demonstrated that
fertility increases in response to severe threats and fear. Given the common
mechanisms impacting fertility, our study elucidates the effects of different
shocks on fertility.

This study also contributes to the literature on the baby boom in a defeated
nation. Unlike various explanations for the United States, Japan’s fertility
rate surge is often attributed to large-scale demobilization (Statistics
Bureau of the Cabinet 1957).444For accounts for the U.S. baby boom, see
Easterlin (1961); Hill (2015); Doepke et al. (2015); Greenwood et al. (2005);
Albanesi and Olivetti (2014); Bailey and Collins (2011). While recent
literature has focused on the impact of gender imbalance on the marriage
market (Ogasawara and Komura 2022) and the restoration of peace due to the
return to normalcy (Igarashi 2022), no studies have addressed the
heterogeneity in the baby boom within the country. Although not our study’s
main focus, we suggest air raids may have contributed to mid-twentieth-century
fertility variations.

The remainder of this paper is organized as follows: Section 2 provides the
historical background of this study. Section 3 elaborates on the potential
mechanisms, our data, and the baseline identification strategy used to
investigate the far-reaching effects on postwar fertility. The estimation
results are presented in Section 4. Finally, Section 5 concludes the paper.

##  2 Background

###  2.1 Air raids on cities

Starting with the first bombardment of the four mainland cities in April 1942,
the Allied Forces launched extensive bombing campaigns against Japanese cities
until August 1945, when Japan surrendered. Between 1942 and 1944, they
predominantly targeted munition factories, such as aircraft manufacturing
plants and military arsenals. However, hit rates remained low due to the
relatively small size of the factories and the influence of weather
conditions. Hence, the Allied Forces shifted their bombing strategies in
January 1945. They believed that the domestic home industry was essential for
Japan to continue the war and began bombarding all cities, including private
houses and small factories engaged in the cottage industry. The large cities
designated as “Selected Urban Industrial Concentrations” were extensively
destroyed by June 1945. Subsequently, even small and medium-sized cities
experienced severe air raids (Okuzumi 2006).

The Kinki region had been consistently targeted by aerial bombardment owing to
the presence of the Hanshin Industrial Zone, a major industrial area in Japan
(Tsujikawa 1992). Osaka, the second-largest city after Tokyo, suffered
significant infrastructure and human losses. Following nighttime attacks that
resulted in approximately 200 casualties in January and February 1945, the
Osaka Air Raid on March 13 obliterated over 130,000 buildings and resulted in
more than 3,000 fatalities. Ultimately, Osaka endured 33 aerial bombings by
the end of the war. After the destruction of the Hanshin Industrial Area, the
Allied Forces carried out precision bombings on military factories in other
cities, such as Akashi, Nishinomiya, and Himeji.555The main targets included
military-related facilities of large companies, such as the Kawasaki Aircraft
Company, Kawanishi Aircraft Company, Toyo Boseki Company, Dai-Nihon Spinning
Company, and Dai-Nihon Celluloid Company. The bombing of the Kawanishi
Aircraft plant in Akashi resulted in the casualties of 74 employees and
approximately 200 civilians in the vicinity of the plant. The principal
facilities were destroyed by June, after which the bombing targets shifted to
residential sections in small- and medium-sized cities (Japanese Air Raid
Compilation Committee 1980).

(a) Number of deaths

(b) Death rate (%)

Figure 1: Human casualties due to air raids in cities in the Kinki region

Notes: The number of deaths from air raids comes from a survey in May 1948,
and the death rates were calculated based on the population in 1947.

Sources: Economic Stabilization Board (1949) and Statistics Bureau of the
Cabinet (1948).

Figure 1 shows human casualties in cities in the Kinki region, sorted by
population in 1947. Population size was a crucial factor in determining
bombing targets, but it did not necessarily determine the scale of
casualties.666The Allied Forces typically targeted cities from the list titled
“Attacks on Small Urban Industrial Areas,” which ranked cities by population
based on the 1940 census. Despite the title, this list included 180 cities,
including major urban centers such as Tokyo and Osaka. While Kyoto, with the
second-largest population in Kinki, experienced relatively few casualties,
Tsu, Akashi, Ashiya, and Kuwana suffered severe damage despite their
relatively small populations. Some cities avoided severe air raids due to
external factors: Kyoto was excluded as a target by the directive of the
Allied Command, Ikeda was mistakenly believed to be outside the flying range
of bombers, and the geographical features of Fuse and Suita were unfavorable
for aircraft radar (Okuzumi 2006).777The reason Kyoto was spared from severe
air raids, despite its large population, remains unclear due to insufficient
evidence. Potential explanations include an intent to preserve its cultural
and historical heritage, such as ancient temples, or consideration as a
potential target city for the atomic bombing (Japanese Air Raid Compilation
Committee 1980, p. 310).

Air raids did not directly target people living outside cities, but they could
have instilled terror in them. The Allied Forces primarily conducted nighttime
attacks to minimize encounters with Japanese forces (Tokyo Air Raid and War
Damage Magazine Editorial Committee 1973). As suburban residents returned home
at night, even if they worked in nearby cities during the daytime, they could
avoid direct damage from air raids. However, those who lived near a bombed
city may have experienced intense fear at the sight of aerial bombardment and
a burning city.888According to Yokoyama (2001), eyewitness accounts indicated
that the air raids on Sakai City and Wakayama City were visible from
approximately 20 km away. A resident of a suburban area described this fear as
follows:

> In general, the people became terrified of the war, and the number of those
> continued to grow who stored their household baggage in air-raid shelters or
> intrusted [sic] it to relatives and friends in the far mountain regions.
> Especially just before war’s end, air-raid warnings sounded morning, noon,
> and night, and there were few people who slept soundly for listening to the
> air-raid reports over the radio. (United States Strategic Bombing Survey
> 1945–1946, p. 35)

Meanwhile, people could only determine the exact extent of damage through
visual confirmation. This occurred because the Imperial General Headquarters
underreported the extensive damage caused by air raids to the public through
radio and newspapers, even though the damage was substantial. Consequently,
people in distant areas believed that the air raids were insignificant and, in
some cases, remained unaware that aerial bombing had taken place. Despite the
tremendous loss of approximately 100 thousand lives in the Great Tokyo Air
Raid on March 10, 1945, the inhabitants of Osaka, located 400 km away from
Tokyo, continued with their lives as usual, harboring little fear of air raids
(Koyama 1985).

###  2.2 Relocation of the population during and after the war

####  2.2.1 Evacuation

The government enacted the Air Defense Law to prevent citizens from leaving
cities and to compel them to participate in firefighting efforts during aerial
bombings.999This law, initially established in October 1937 to mitigate the
damages from air raids, underwent revisions in response to changing wartime
circumstances. In November 1941, it incorporated measures anticipating air
raids, including the prohibition of evacuation from cities, the obligation to
engage in emergency firefighting during air raids, and the imposition of
stricter penalties. The prohibition on leaving cities was enforced through the
mutual monitoring of neighborhood groups known as tonarigumi, and those who
violated this rule faced imprisonment or fines. Additionally, local
authorities frequently employed threats, such as removing individuals from the
community register and discontinuing rations, to dissuade residents from
attempting to seek refuge (Mizushima and Omae 2014, p. 12). Being labeled as
unpatriotic for abandoning civic duties also functioned as a form of social
censure, further discouraging escape.

Some residents were granted exceptions and allowed to evacuate from cities.
This included individuals who lived in or worked in buildings scheduled for
demolition as part of building evacuations, victims of air raids, and people
residing in cities where evacuation was recommended under the Urban Evacuation
Implementation Guidelines established in December 1943.101010Regarding
building evacuations, approximately 610,000 buildings were demolished to
create fire-blocking belts in 279 cities during WWII. Following the Osaka Air
Raids, priority was given to the victims of air raids. These individuals were
directed to designated evacuation sites located in neighboring prefectures,
such as Nara and Shiga, rather than to nearby towns and villages (Japan War
Damaged Bereaved Association 2002).  These guidelines were applied to 11
cities, including Osaka, Kobe, and Amagasaki in the Kinki region. In March
1944, the government strongly recommended the evacuation of specific groups in
these cities, such as older individuals (65 years and older), young children
(elementary school students and younger), pregnant women, and individuals with
illnesses, as they could hinder firefighting efforts during air raids
(Mizushima and Omae 2014, p. 73).

However, during the wartime period, all evacuations required a license issued
by the city office, limiting people’s freedom to relocate. Moreover, those who
wished to evacuate were required to find an evacuation destination on their
own, usually relying on relatives living in rural areas. Furthermore, with the
growing demand for evacuation, city offices ceased issuing licenses to civil
servants, factory workers, and other essential workers who were crucial to
maintaining city functions, even in cities where evacuation was recommended.
Consequently, only a limited portion of the population could evacuate from
these cities.

####  2.2.2 Demobilization and repatriation

In the postwar period, numerous demobilized soldiers and Japanese residents
returned from overseas territories, including Manchuria, Taiwan, and the
Korean Peninsula. By the end of 1949, the number of returnees had exceeded six
million (Repatriation Relief Agency 1950, p. 12).111111Nevertheless, an
estimated 376,929 people were still left behind at this time. These
unrepatriated people decreased to 63,042 by 1955 (Repatriation Relief Agency
1963, p. 162). Upon their return, these individuals usually went back to their
hometowns or the homes of relatives. Limited available data suggests that
demobilized and repatriated people represented approximately 2–4% of the
population in cities and 7% in counties across the Kinki region.121212In Shiga
Prefecture, they accounted for 7% of the population in both Otsu City and Gamo
County and 3–4% in other cities and counties as of October 1947 (Shiga
Prefecture 1950, p. 39). In Hyogo Prefecture, as of March 1949, the percentage
was only approximately 2% across various cities and counties, with the
exception of 7% (Hyogo Prefecture 1952, pp. 70–71).

Prefectural governments encouraged returnees whose hometowns were destroyed by
air raids and who had no relatives to support to move to temporary shelters or
settlements and engage in agriculture (Repatriation Relief Agency 1950, pp.
89–90). For instance, in Wakayama Prefecture, 669 households settled in
designated areas and cultivated their land between 1945 and 1947 (Wakayama
Prefecture 1950, p. 114). Nara Prefecture also promoted this welfare project,
receiving 334 and 114 families in 1946 and 1947, respectively, (Nara
Prefecture 1951, p. 137). In 1947, the government of Shiga Prefecture
authorized the settlement of 569 households to cultivate agricultural land
(Shiga Prefecture 1950, p. 86). According to Yasuoka (2014, pp. 162–163),
those who arrived in the postwar period were more likely to settle compared to
those who came for evacuation during the war, at least in the case of Kyoto
Prefecture.

In addition to the utilization of uncultivated land in rural areas, former
military lands that the GHQ had not confiscated in cities were also converted
into settlements. Furthermore, prefectural governments allocated people to
settlements in groups of 10–-100, ensuring that the population did not
concentrate in one place despite the significant influx of returnees.

####  2.2.3 Labor mobilization and transfer

In addition to evacuation and return, labor mobilization could have led to
population relocation. Owing to the shortage of male labor during wartime, the
government forcibly mobilized unmarried women and workers from non-essential
industries into war-related sectors. Consequently, the population may have
temporarily relocated, while the evacuation of workers was restricted.
Nevertheless, the impact on rural areas was likely limited because the
agricultural sector was mostly excluded from mobilization to ensure an
adequate food supply.131313Male agricultural workers were also mobilized into
military industries in the early stages of the war, when there was still spare
capacity to produce food. Consequently, in conjunction with conscription, the
proportion of female labor increased in the agricultural sector during the
war.

Figure 2 shows industry-specific worker numbers from wartime to postwar. With
the decline in the total labor force during the war, the proportions of
workers in commerce, domestic services, and other industries decreased.
Conversely, the mining, manufacturing, transportation, and communication
industries saw an increase in their shares. These trends indicate labor
concentration in the military and aviation-related industries due to
mobilization. The number of workers in the agricultural and forestry sectors
remained steady, implying that there was little demographic impact of labor
mobilization in rural areas.

Figure 2: Trends in labor force by industry

Notes: The labor forces were based on surveys in October 1940, February 1944,
May 1945, and October 1947. Sources: Umemura (1988, p. 259).

Despite the war ending, severe food shortages persisted until 1947 (Shimizu
1994). Consequently, rural farmers preferred to continue farming on their
traditional lands rather than leaving their villages to pursue opportunities
in other industries. Although Fig. 2 indicates an increase in the labor force
in the agricultural sector after the war, this increase was primarily due to
the participation of returnees. Most of these returnees were individuals who
transitioned to full-time farming, as opposed to their earlier status as part-
time farm household members who earned their main income from jobs in other
industries. This shift to full-time farming was necessitated by the
destruction of factories by air raids and the collapse of the urban labor
market following the war’s end (Statistics Department of Ministry of
Agriculture and Forestry 1946). Furthermore, while the demand for agriculture
was driven by the insufficient food supply, limitations on available farmland
made it difficult for people to relocate to rural areas and engage in farming.
Therefore, despite the statistical change in the labor force in the
agricultural industry, the fundamental nature of farmers remained relatively
unchanged throughout both wartime and the immediate postwar period. This
suggests that population outflow from rural areas was a rare occurrence.

####  2.2.4 Population change before and after air raids

(a) 1945

(b) 1947

Figure 3: Percentage change in population compared to 1944 in Osaka Prefecture

Notes: The positive change rate indicates an increase relative to the
population in February 1944, before the air raids intensified. The data were
based on surveys in November 1945 and October 1947. Areas surrounded by thick
lines denote cities. The population is aggregated according to the 1950
municipal divisions. Sources: Osaka Prefecture (1951, pp.46–59) and the
Ministry of Land, Infrastructure, Transport and Tourism
(https://nlftp.mlit.go.jp/ksj/index.html, accessed on July 25, 2021).

To summarize the population relocation, the limited number of people permitted
to evacuate did not move to neighboring towns and villages but dispersed,
relying on their relatives. When the war ended, they gradually returned from
their evacuated homes to their own cities. Although there were many
demobilized soldiers and returnees from overseas territories after the war,
they did not congregate in one specific area. Additionally, there was little
rural-to-urban migration during both the wartime and immediate postwar
periods.

Despite being a limited case study, historical data from Osaka, the only
prefecture with municipality-level population data available before and after
the air raids, corroborate these population changes. Figure 3 shows the
population changes in Osaka relative to 1944, the year before the air raids
commenced. In 1945, immediately after the air raids, the population dropped by
up to 0.8% in cities marked by thick lines on the map, while the population
increased in all towns and villages. This significant population increase in
areas far from cities contradicts the notion of evacuation to areas closer to
cities and the population outflow from rural areas.

In 1947, the urban population exhibited a recovery trend, indicating a
temporary exodus from cities and the return of demobilized soldiers,
repatriates, and evacuees.141414For example, owing to intense air raids, Osaka
City’s population declined from 2,883,344 in 1944 to 1,102,959 in 1945. The
population recovered to 1,559,310 by 1947 (Osaka Prefecture 1951, pp. 46–59).
Furthermore, the rate of population change was similar across towns and
villages. Thus, the spatial distribution of the population reverted to the
pre-air raid distribution, indicating no significant population concentration
near cities when comparing the pre-war period with 1947.

##  3 Empirical framework

###  3.1 Potential mechanisms

We discuss three potential factors contributing to the far-reaching effects of
the bombings on postwar fertility rates.151515Rigorous identification of all
mechanisms falls outside the main scope of this study. Additionally, we focus
on fertility changes during the postwar period rather than during the war. The
most intuitive factor is the threat and corresponding fear caused by air
raids. This factor is a motivational factor for behavioral responses to
violent incidents (Williams et al. 2012). Even in towns and villages without
direct damage, the sense of threat to oneself or one’s family may have
resulted in a decline in childbirth during the war. Couples may have delayed
childbearing due to challenges in emergency evacuating pregnant women and
young children. Furthermore, military conflicts can induce psychological
stress that can lead to reduced reproductive behaviors (Kidane 1989). In areas
with neighboring cities experiencing air raids and severe damage, people might
lose their desire for reproduction. Psychological stress can adversely affect
reproductive capacity (Frankenberg et al. 2014; Nargund 2015). If childbirth
were postponed due to these mechanisms during wartime, fertility rates could
rebound after the war. Hence, the threat of air raids could potentially have
increased fertility in the postwar period.

Additionally, psychological theories support the idea that the fear of air
raids in neighboring cities affects fertility. Terror management theory
suggests that a strong fear of violence can lead individuals to align with
traditional values, like having more children and starting families (Rodgers
et al. 2005; Solomon et al. 2000). Attachment theory indicates that couples
may seek greater proximity in response to threats such as disasters,
reflecting attachment needs and potentially increasing fertility (Cohan and
Cole 2002; Hazan and Shaver 1994). These behavioral changes due to
psychological reactions can persist when individuals are exposed to intense
fear (Rodgers et al. 2005). Therefore, psychological theories suggest that
whether the birth rate remains high or declines in the postwar period depends
on the intensity of fear experienced during the air raids.

Another significant factor is the increase in socioeconomic insecurity
attributed to air raids in neighboring cities. However, the theoretical
predictions regarding the effects of instability on fertility are
inconsistent. Increased instability can make childrearing more challenging,
causing people to avoid having children. The mechanism of delayed childbirth
has also been interpreted from an economic perspective. When parents expect
their children to provide financial support in old age, childrearing is seen
as an irreversible and long-term investment (Aassve et al. 2021; Comolli
2017). Insecurity makes such an investment riskier; therefore, couples are
likely to postpone childbirth until after the war ends, potentially resulting
in an increased birth rate during the postwar period. Conversely, economic
insecurity can enhance the value of economic support from children (Cain
1983). Before the mechanization of the agricultural sector, children were a
crucial labor force in rural areas from a young age. Thus, unless there is a
clear increase in the risk of death, couples might choose to have more
children during the war. Consequently, the fertility rate could decrease after
the war.161616 When child mortality increases and remains high for a long
time, couples may have more children as a precaution to ensure that the
desired number of children survives (Frankenberg et al. 2014; Verwimp and Van
Bavel 2005; Iqbal 2010). This relationship between child mortality occurring
outside the family and fertility decisions is known as the “extrafamilial
effect” (Nobles et al. 2015). In summary, insecurity can have both positive
and negative effects.

One specific potential factor is an increase in nationalism, which can ensure
compliance with national population policies. Starting in 1939, the Japanese
government advocated population policies aimed at increasing the population,
popularly known as “umeyo fuyaseyo” (Beget and Multiply), to secure enough
soldiers. Moreover, given that air raids could boost national morale (Jones et
al. 2006, 2004), those who directly witnessed bombings would likely have
enhanced their morale compared to those who only learned about underreported
casualties through newspapers and radio. Therefore, inhabitants of towns and
villages neighboring bombed cities might have actively followed the national
policies, striving to have more children during the war due to rising
nationalism.171717In Japan during WWII, patriotic behaviors were highly
esteemed. The special attack corps that sacrificed their lives by launching
bodily attacks on their targets, known as kamikaze, symbolized the values of
that time. This increase in fertility would have ended with a defeat, limiting
the postwar increase in fertility relative to other areas.

However, the mechanism involved in nationalism and patriotism was observed
only in areas that did not suffer from intense fear. This is because severe
air raids shatter people’s will and evoke avoidance responses to threats of
harm and fear, rather than actions motivated by high national morale (Gregor
2000; Jones et al. 2006). This finding is consistent with the Japanese
experience. According to a survey report titled “THE EFFECTS OF STRATEGIC
BOMBING ON JAPANESE MORALE” in United States Strategic Bombing Survey
(1945–1946), air raids profoundly affected Japanese civilians’ hopes, fears,
aspirations, sense of security, and attitude.181818The United States Strategic
Bombing Survey conducted a sample survey between November 10 and December 29
to assess the impact of the bombings on morale. Using a two-stage sampling
method to reduce sample selection bias, this survey involved 3,150 Japanese
civilians aged 16–-70 years living in Honshu or western Kyushu (the main or
southwestern islands of the Japanese archipelago). The first stage of sampling
covered 86% of the population, and 76% of those selected in the second stage
eventually participated in the survey interviews. In this survey, 41% of
respondents reported that they were most worried about air raids during the
war. For them, air raids were a more immediate threat than military defeats in
the far-off Pacific Islands. A Kyoto city official made the following
statement: “(in the respondent’s area) in the last year of the war there was a
marked changed in the emotional status of most people. Many became irritable,
unstable, and critical of each other. . . . Word had gotten out that Kyoto
would be wiped out by bombs and there was a near panic” (United States
Strategic Bombing Survey 1945–1946, p. 35). Additionally, the belief that
Japan was winning the war because of false public announcements intensified
people’s sense of despair after the air raids. Air raids accounted for 32% of
the factors that convinced rural inhabitants that Japan would lose the war
(United States Strategic Bombing Survey 1945–1946, p. 48). Conversely, 43%
felt better off after the war, primarily due to the cessation of air raids
(United States Strategic Bombing Survey 1945–1946, p. 22). These survey
results corroborate the fact that the threat of air raids likely outweighed
any increase in morale.

###  3.2 Data

For the empirical analysis, we compiled WWII bombing damage and demographic
data to create Kinki region town/village panel data for 1935 and 1947. The
Kinki region is ideal for studying bombing impacts owing to its cities’
diverse damage.191919It offers a higher variability of damages compared to
other regions, making it more suitable for analysis. For instance, the Tohoku
region was less affected by air raids because of its distance from the bases
of the Allied Forces. In contrast, in the Kanto region, air raids against
Tokyo City were devastating compared to other cities. Additionally, the Kinki
region was spared from the atomic bombing, which could have different effects
on fertility outcomes compared to conventional bombing.202020The atomic
bombings were targeted at Hiroshima City in the Chugoku region and Nagasaki
City in the Kyushu region. These cities experienced a high death toll, with
estimated death rates of 23.2% in Hiroshima and 8.8% in Nagasaki among the
1944 population (Nakamura and Miyazaki 1995, p. 283). We chose the years 1935
and 1947 as they represent the period just before and after WWII,
respectively, for which reliable demographic data are available.

To calculate the distances from each town or village to the cities, we used
administrative divisions from 1950 because 1947 divisions were
unavailable.212121 Geographical information on the administrative divisions
was obtained from the Ministry of Land, Infrastructure, Transport, and
Tourism’s download website (https://nlftp.mlit.go.jp/ksj/index.html, accessed
on July 25, 2021). The distances were computed based on the position of the
center of gravity. As Osaka, Kyoto, and Kobe have very large areas, we used
the center of gravity of their closest districts when calculating the
distances to these cities. If towns and villages adjoined a city, the distance
was considered zero. Hence, the variables were aggregated based on the 1950
divisions. While some observations were omitted because of municipal mergers,
our sample consists of 1,437 towns and villages, covering approximately 95% of
the 1,526 towns and villages in the Kinki region at that time. This
comprehensive dataset helps mitigate concerns related to sample selection
bias. Our sample did not include cities because we focused on the far-reaching
indirect effects of bombings rather than their direct effects.

The main source of our data on bombing damage is Economic Stabilization Board
(1949), who compiled human and building damages caused by air raids,
categorized by damage scale in each city. This source is considered the most
reliable for air raids in Japan. The data reported in United States Strategic
Bombing Survey (1945–1946) are widely used (for example, Davis and Weinstein
2002), but they only include casualties in the targeted cities of the Allied
Forces.222222However, the Economic Stabilization Board might have slightly
overestimated the casualties because their purpose was to receive amnesty for
wartime reparations by reporting wartime damage. Therefore, we conducted
additional estimates based on other data sources: the “Final Reports of
Records of the U.S. Strategic Bombing Survey” in United States Strategic
Bombing Survey (1945–1946) and the “List of Casualties from Air Raids on War
Damaged Cities in Japan” in Association of War-Devastated Cities (1962, pp.
71–72). The estimation results remain unchanged, supporting the validity of
the main results. See Online Appendix B for further details and other
robustness checks. We adopted the number of deaths from bombings as a measure
of the intensity of the war damage. Using the distances to bombed cities and
their death tolls, we calculated the total number of deaths due to bombings at
various distances from each town or village.232323Focusing on carpet bombings
on civilians, we exclude damages in cities where only precision bombings on
military facilities and plants were carried out, even if there were
unfortunate deaths. Consequently, the number of deaths in Suzuka, Kainan, and
Nara was regarded as zero. However, our estimation results remain unchanged if
we include the damage in these cities (not reported). This is our key
independent variable for capturing the far-reaching effects of bombings on
postwar fertility.

For demographic data at the municipality level in 1935 and 1947, we obtained
male and female populations from the Population Census of Japan (Statistics
Bureau of the Cabinet 1939, 1948), and the number of live births from the
Vital Statistics of Japan by Municipalities (Statistics Bureau of the Cabinet
1938, 1949). These data sources were based on population census
data.242424Despite the chaos of war, the government accurately captured the
population because the registration of the resident register was required to
receive rationed foods and goods, which were essential for living at that time
(Repatriation Relief Agency 1950, p. 89). Our outcome measure of fertility
level was the crude birth rate, defined as the number of live births per 1,000
people. We also used the log of the population and the male-to-female sex
ratio as the main control variables. Table 1 presents summary statistics for
these variables.

Table 1: Summary statistics

| Mean | Std. Dev. | Min | Max | Observations
---|---|---|---|---|---
Crude birth rate | $31.80$ | $4.89$ | $10.12$ | $56.63$ | $2,874$
Sex ratio | $0.97$ | $0.08$ | $0.56$ | $2.00$ | $2,874$
lnPopulation | $8.03$ | $0.58$ | $5.57$ | $10.28$ | $2,874$
Proximity to city | $0.59$ | $0.49$ | $0$ | $1$ | $2,874$
City population | $7.39$ | $6.27$ | $0.00$ | $15.98$ | $2,874$
Death toll from bombing in nearby cities (only non-zero values)
$\leq$ 5 km | $1,413.35$ | $2,797.71$ | $1$ | $10,663$ | $207$
$\leq$ 10 km | $2,155.59$ | $3,603.63$ | $1$ | $18,172$ | $355$
$\leq$ 15 km | $2,499.21$ | $3,996.18$ | $1$ | $18,432$ | $577$
$\leq$ 20 km | $2,707.69$ | $4,208.79$ | $1$ | $19,888$ | $808$
$\leq$ 25 km | $3,316.16$ | $4,682.16$ | $1$ | $19,888$ | $974$

Notes: Crude birth rate is defined as the number of live births per 1,000
population. The sex ratio is calculated as the number of men divided by the
number of women. Proximity to the city is the dummy variable, taking one if
there was at least one city within 15 km. The city population is defined as
the inverse hyperbolic sine of the total population of cities within 15 km.
Sources: Economic Stabilization Board (1949); Statistics Bureau of the Cabinet
(1939, 1948, 1938, 1949).

###  3.3 Baseline identification strategy

This case study of Japan during WWII offers the following advantageous
settings: First, bombing targets and damages were determined independently of
any characteristics of the surrounding towns and villages, even if they
correlated with some determinants of the fertility rate in bombed cities.
Moreover, many factors created variance in the magnitude of damage to cities
(Davis and Weinstein 2002). Thus, this exogenous treatment enables us to
estimate the far-reaching effects of bombings on the postwar crude birth rate
in towns and villages without being disturbed by other confounding factors,
such as the number of demobilized soldiers. The exogeneity also relaxes the
common trend assumption in our analysis.

Second, the geographical location of mainland Japan as an island nation in the
Far East inherently limited the Allied Forces’ modes of aggression almost
exclusively to aerial bombardment.252525 The Allied Forces landed only in
Okinawa Prefecture during WWII. Naval bombardment hit several cities on the
mainland but caused negligible damage, accounting for only 0.5% of the total
bombing damage (Nakamura and Miyazaki 1995, pp. 278, 284). Considering that
only Shingu City suffered such attacks in the Kinki region, our analysis
focused on air-raided damage.  In continental nations or regions, adversarial
forces have the option of invading a target city through other land
territories, which may directly affect fertility rates in areas along the
path. Additionally, when a nation is subjected to a multitude of assault
methods, the effects on fertility can vary depending on the attack type, even
if the measured damage sizes are identical. Japan’s wartime damage, limited to
air raids, avoids these possibilities and ensures the validity of our
empirical analysis. The relatively short period of air raids against the
entire city, spanning only from early 1945 to the end of the war, is also
beneficial for our analysis because the influence of war damages on decision-
making regarding childbirth might change as the war drags on (Iqbal 2010).

Finally, the information control exercised by the Japanese government during
wartime prevented the spread of indirect mental shocks due to air raids
nationwide, which helps us identify the far-reaching effects. With the
intention of maintaining national morale, official narratives markedly
overstated military success and understated domestic casualties. Consequently,
populations residing at a considerable distance from bombed cities remained
largely uninformed of air raids and thus were not influenced by them. In
contrast, those close to bombed cities could see and hear the firsthand
destruction caused by aerial bombardment. Therefore, bombings were likely to
have more potent indirect effects on areas closer in proximity but did not
affect areas that were too far away. This relationship between proximity and
the magnitude of the effects enables us to distinguish the localized impacts
of air raids from national-level macro shocks.

To investigate the far-reaching effects of war damage on fertility, we employ
a fixed-effects model in the spirit of the DID approach. Our baseline model is
as follows:

$\displaystyle\textit{CBR}_{it}=\alpha+\beta(\textit{Bombing}_{i}\times\textit{Postwar}_{t})+\gamma\textit{Postwar}_{t}+\mathbf{x}^{\prime}_{it}\bm{\delta}+\nu_{i}+\varepsilon_{it}$
(1)

In the equation above, $i$ represents towns and villages numbered from 1 to
1,437, and $t$ represents the years 1935 and 1947. The dependent variable
$\textit{CBR}_{it}$ stands for the crude birth rate. $\textit{Bombing}_{i}$
indicates the intensity of air raids in neighboring areas during WWII,
measured by the number of deaths (in thousands) from bombings in cities within
15 km. $\textit{Postwar}_{t}$ is a dummy variable that equals one if the year
is 1947, representing the year-fixed effect. The interaction term
$\textit{Bombing}_{i}\times\textit{Postwar}_{t}$ captures the far-reaching
effects of bombing on postwar fertility. $\mathbf{x}^{\prime}_{it}$ is a
vector of control variables, $\nu_{i}$ represents town and village fixed
effects, and $\varepsilon_{it}$ is a random error term. The year-fixed effect
controls for all year-specific unobservable confounders, allowing us to
identify the indirect effects of the bombings without being influenced by
national level macro shocks, including those related to the war. Additionally,
town and village fixed effects account for heterogeneity across
municipalities.

A potential concern in our empirical context is that many individuals who fled
from bombed cities may have sought refuge in neighboring villages and
established their homes there. If a direct experience of air raids altered
their desired number of children, our key variable could potentially encompass
a combination of both direct and indirect effects of bombings. Additionally,
returnees might have chosen to settle in proximity to cities. These concerns
contrast with historical evidence, which suggests that people evacuated or
returned to the countryside where their relatives resided rather than to
nearby rural areas. Nonetheless, we address this possibility by incorporating
the male-to-female sex ratio and the logarithm of the population as control
variables in our estimation model. These variables help account for the impact
of population relocation and demographic characteristics on our
analysis.262626For additional insights, Ogasawara and Komura (2022) has
emphasized the importance of considering the role of sex ratio in assessing
the effects of demobilization on fertility rates.

Another issue to consider is the geographical proximity to a city. The
definition of the bombing damage variable inherently assigns a value of zero
to towns and villages far from any city. In contrast, for observations in
close proximity to cities, this variable takes a positive value if the nearby
city is subjected to bombing and zero otherwise. Therefore, our estimates
could be biased if the impact of geographical proximity on birth rates varied
after the war.272727 For instance, male workers in rural areas near cities
might have had higher mobility. The decline in the male labor force could have
placed an additional burden on female agricultural workers, leaving them with
little capacity to bear and raise children. The challenge women faced in
balancing agricultural responsibilities with childbearing and child-rearing
during that period is supported by the research finding of Okado and
Yanagisawa (1996), which indicates that infant mortality rates increased in
households with larger expanses of arable land.  To address this potential
confounding factor, we introduce an interaction term into our estimation model
as a control variable. This term combines a dummy variable, set to one if a
city is located within a 15-kilometer radius (Proximity to city), with the
postwar dummy variable. Additionally, larger cities might have had a more
significant influence on neighboring towns and villages. To account for this
concern, we adopt an estimation equation that controls for the total
population of cities within 15 km, replacing the proximity dummy.282828When
taking the natural logarithm of the city population, we apply the inverse
hyperbolic sine transformation (i.e., ln$(x+\sqrt{x^{2}+1})$ for a random
variable $x$) to retain observations whose value is zero. These adjustments
ensure that we consider the potential influence of geographical proximity on
our analysis, particularly with regard to postwar birth rates.

##  4 Estimation results

###  4.1 Baseline results

Table 2 presents these results of our analysis. In column (1), we observe the
regression of the crude birth rate on the key independent variable, bombing
damage. In column (2), we introduce the sex ratio as an additional control
variable, and in column (3), we include the log of the population. Our
baseline specification, found in column (4), encompasses the sex ratio, log of
population, and a dummy variable representing proximity to a city. This
specification maintains town and village fixed effects and postwar dummy
variables. Column (5) displays the results when we incorporate the population
of nearby cities instead of the proximity dummy. Once again, town and village
fixed effects and postwar dummy variables are included in all specifications.

In column (1), we observe that the estimated coefficient of the interaction
term between bombing damage and the postwar dummy variable is not only
positive but statistically significant at the one percent level. This result
indicates that air raids in neighboring cities during WWII had a discernible
impact on the crude birth rate in towns and villages during the postwar
period. This aligns with our hypothesis that war damage indirectly influences
fertility in areas not directly affected but near damaged regions. Columns (2)
and (3) demonstrate that the estimation results remain consistent even when we
control for demographic variables such as the sex ratio and population. These
findings confirm the reliability of our results.

Column (4) maintains a significantly positive estimated coefficient for the
key independent variable, while the proximity dummy’s coefficient is positive
but statistically insignificant. These results suggest that the relationships
between bombing damage and crude birth rates are not due to geographical
proximity to a city but rather stem from the far-reaching effects of air
raids. Our baseline results indicate that for every 1,000 additional deaths
caused by air raids within a 15-kilometer radius, the crude birth rate
increased by 0.245 permil in 1947. Replacing the proximity dummy with the
nearby cities’ total population in column (5) yields consistent estimation
results. Hence, the size of nearby cities does not seem crucial for pre- and
post-WWII fertility rates.

Table 2: Effects of bombing damage within 15 km on fertility

| (1) | (2) | (3) | (4) | (5)
---|---|---|---|---|---
Bombing$\times$Postwar | 0.234*** | 0.234*** | 0.268*** | 0.245*** | 0.218***
| (0.047) | (0.047) | (0.054) | (0.055) | (0.099)
Sex ratio |  | 1.177 | 2.091 | 1.956 | 2.0030
|  | (2.770) | (2.844) | (2.848) | (2.839)
lnPopulation |  |  |  $-$1.965 |  $-$2.276 |  $-$2.269
|  |  | (1.497) | (1.531) | (1.531)
Proximity to city$\times$Postwar |  |  |  | 0.541 |
|  |  |  | (0.359) |
City population |  |  |  |  |  $-$0.280
|  |  |  |  | (1.137)
City population$\times$Postwar |  |  |  |  | 0.045
|  |  |  |  | (0.033)
Town and village fixed effects | Yes | Yes | Yes | Yes | Yes
Postwar fixed effect | Yes | Yes | Yes | Yes | Yes
Observations | 2,874 | 2,874 | 2,874 | 2,874 | 2,874

Notes: The dependent variable is the crude birth rate (permil). The
independent variable Bombing is the number of deaths (in thousands) due to the
bombing in cities within 15 km. The Sex ratio is the male-to-female sex ratio,
the lnPopulation is the log of population, the Proximity to city is the dummy
variable taking one if there were cities within 15 km, and the City population
is the inverse hyperbolic sine of the total population of cities within 15 km.
***, **, and * represent statistical significance at the 1%, 5%, and 10%
levels, respectively. Standard errors clustered at the town–village level are
in parentheses.

###  4.2 Geographical extent of effects

To explore the geographical reach of fertility effects, we assessed bombing
damage impact at different distances. The estimating equation used here is
consistent with the baseline specification used in column (4) of Table 2, but
it employs varying distances to capture the effects of bombing instead of the
fixed 15-kilometer radius. Figure LABEL:fig:res_main illustrates the results,
with the dotted line representing the estimated coefficient of the total death
toll (in thousands) from air raids in cities within 5, 10, 15, 20, and 25 km,
all of which were positive. Furthermore, the solid lines depicting the 90%
confidence intervals indicate that the results hold statistical significance
at all distances. These findings are consistent with the baseline results,
affirming the presence of far-reaching effects of bombing on fertility. The
declining coefficients imply that air raids had a more pronounced impact on
fertility in towns and villages near bombed cities.

We also estimated the effects of bombings in cities within 0–5, 5–10, 10–15,
15–20, and 20–25 km to explore the detailed relationship between distance to
air raids and their impact. However, the impact at a particular distance might
have varied based on the severity of bombing damage in closer cities. For
instance, the effect of bombing within 5–10 km may have been smaller in towns
and villages that experienced severe air raids within five km. To address
this, we controlled for bombing damage within a shorter distance. Thus, when
we estimate the effect of bombings within 10–15 km, the estimation equation
includes bombing damages within 10 km. The results are presented in Figure
LABEL:fig:res_sub. The estimated coefficient of bombing damage remained
significantly positive at distances of 5–10 km and 10–15 km, while those at
15–20 km and 20–25 km were statistically insignificant. These findings imply
air raids influenced the birth rate within 15 km but showed no significant
effects beyond.

The estimation results are shown in Figs. LABEL:fig:res_main and
LABEL:fig:res_sub are complementary. Although Fig. LABEL:fig:res_main shows
significant results at all distances, it does not provide specific insight
into whether air raids within the extended distances had significant effects.
For instance, the estimated effect within 25 km, although significant, may
have been influenced by bombings within 5 km. The analysis results presented
in Fig. LABEL:fig:res_sub address this issue. In contrast, using graded
distances prevents us from estimating comprehensive effects. Thus, Fig.
LABEL:fig:res_sub does not encompass the effects of air raids within distances
shorter than the specified range. To counterbalance this limitation, we rely
on estimates in Fig. LABEL:fig:res_main. Therefore, it is essential to
interpret both sets of results in tandem. These combined findings indicate
that air raids within 15 km significantly influenced the postwar crude birth
rate.

###  4.3 Heterogeneity in effects

We also investigated the heterogeneity of the far-reaching effects of air
raids. While our baseline model assumes linearity, the effects of bombings may
vary depending on damage intensity. Thus, we introduced a categorical variable
representing clusters of damage intensity to capture these heterogeneous
effects. The estimation equation is as follows:

$\displaystyle\textit{CBR}_{it}=\alpha+\sum_{k=1}^{5}\beta_{k}(C_{ki}\times\textit{Postwar}_{t})+\gamma\textit{Postwar}_{t}+\mathbf{x}^{\prime}_{it}\bm{\delta}+\nu_{i}+\varepsilon_{it}$
(2)

where $C_{ki}$ is an indicator variable that takes on a value of one if
$\textit{Bombing}_{i}$, which represents the number of deaths (in thousands)
due to bombings in cities within 15 km of $i$ is classified into the $k$-th
cluster of the damage intensity. The first to fifth clusters consist of death
tolls of 1–26, 81–269, 416–881, 1,271–1,895, and 6,789–18,432,
respectively.292929These clusters are generated by the k-means clustering
algorithm, with quintile groups as the initial clusters for repeatability. The
estimated parameter $\hat{\beta_{k}}$ is interpreted as the mean effect of
bombings on the crude birth rate in the $k$-th cluster, reflecting the
heterogeneity of the effects depending on the damage intensity.

Figure 4 shows the results estimated using Equation (4), in which the control
variables include the sex ratio, population, and proximity dummy. The
significant positive effect at the strongest intensity corresponds to our
baseline results. However, the effects in the other clusters were negative.
This result difference suggests that the bombing’s far-reaching effects on the
crude birth rate varied with the scale of damage. Small-scale air raids may
have negatively impacted postwar fertility, while large-scale air raids may
have had a positive influence.

Figure 4: Effects of bombing on fertility by damage size within 15 km

Notes: The dotted and solid lines indicate the point estimates and their 90%
confidence intervals, respectively. The dependent variable is the crude birth
rate (permil). The key independent variables are the dummy variables
representing each cluster of bombing damage intensity within 15 km (1–26,
81–269, 416–881, 1,271–1,895, and 6,789–18,432 deaths), interacting with the
postwar dummy variable. The numbers of observations in each cluster are 320,
232, 130, 224, and 248, respectively. The control variables are the male-to-
female sex ratio, the log of population, and a dummy variable representing
proximity to a city. The town and village fixed effects and postwar dummy are
also included. A robust standard error is clustered at the town–village level.

The different effects imply distinct channels by which bombing indirectly
impacted nearby postwar fertility. While the role of insecurity is ambiguous
because of its potential positive and negative effects, these results align
with the mechanisms of threat and nationalism. Relatively small-scale air
raids could have bolstered nationalism but might not have posed a major
threat. Hence, wartime population policies promoting childbirth may have led
to a postwar fertility rate decrease. In contrast, large-scale air raids
instilled fear in people and destroyed national morale, leading to a positive
impact on postwar fertility.

The mean effect for the first to fourth clusters was $-1.507$, roughly
equivalent to 4.74% of the sample mean crude birth rate. While this is
interpreted as a negative, far-reaching effect of the bombing, the treatment
group is inevitably affected by proximity to a city. Given that the estimated
coefficient of the proximity dummy variable is 1.603, the combined effects
amount to 0.096. This calculation suggests that the adverse, far-reaching
effect on postwar fertility offsets the positive impact of unobservable
factors associated with proximity. For the cluster with the most severe
damage, the total effect was calculated as 2.844, which is approximately 8.94%
of the mean crude birth rate in our sample. The magnitude of this effect is
over 10 times larger than the estimated coefficient of 0.275 for the postwar
dummy, indicating the significant roles of air raids and city proximity in
shaping postwar fertility, even in undamaged areas.

###  4.4 Quasi-experimental approach

To clarify distinctions in far-reaching effects through potential channels, we
use a quasi-experimental approach based on Allied Forces flight paths. They
flew from military bases in the Mariana Islands, southeast of Japan, when
bombing Japanese cities.303030A typical flight path of the Allied Forces is
displayed in Online Appendix A. Hence, those in the southeast likely felt
heightened fear due to visible bombers and frequent air-raid sirens. However,
other potential mechanisms, like increased insecurity and shifts in national
morale, were unrelated to neighboring bombed city directions. Given the
exogenous factors of Allied Forces’ departure direction and town/village
locations, we can assess bombing’s far-reaching fertility effects through the
lens of threat and fear, using the direction from bombed cities.

The analytical model that incorporates the direction is presented as follows:

$\displaystyle\textit{CBR}_{it}=\alpha+\beta(\textit{Bombing}_{i}\times\textit{Postwar}_{t}\times
I_{di})+\gamma\textit{Postwar}_{t}+\mathbf{x}^{\prime}_{it}\bm{\delta}+\nu_{i}+\varepsilon_{it}$
(3)

Here, we use $d=1,...,360$ to represent the direction angle. The indicator
variable $I_{di}$ takes on the value of one if a town or village $i$ is
located within a range of $d\pm 22.5$ degrees of the nearest bombed city. The
link between bombing damage and direction is not strictly deterministic
because direction is determined solely based on the location of the nearest
bombed city, whereas damage accounts for the total damage in all cities within
15 km. Nevertheless, our estimates effectively capture the overall trend of
far-reaching effects based on direction. The control variables and fixed
effects remain consistent with those in the baseline specifications.

Figure 5: Effects of bombing on fertility by direction from the nearest city

Notes: The solid and dashed lines indicate the point estimates and their 90%
confidence intervals, respectively. Two villages surrounded by cities or the
sea in all directions are excluded. The dependent variable is the crude birth
rate (permil). The key independent variable Bombing is the number of deaths
(in thousands) due to the bombing in cities within 15 km, which is interacted
by the postwar dummy and indicator variables representing the angle of
direction from the nearest city (including $\pm 22.5$ degrees). The control
variables are the male-to-female sex ratio, the log of population, and a dummy
variable representing proximity to a city. The town and village fixed effects
and postwar dummy are also included. A robust standard error is clustered at
the town–village level.

Figure 5 shows a visualization of the results in all directions. The analysis
revealed three distinct groupings of the estimated effects on fertility based
on geographical orientation. First, we observed positive and statistically
significant effects between the South and East. Second, positive but
statistically insignificant relationships were found between the East and
North, as well as between the West and South. Finally, negative impacts were
identified between the North and West.

These findings align with our hypothesis, derived from potential mechanisms
and varying damage intensity interpretations. The significantly positive
effects on the southeastern side, directly under the flight paths, support the
idea that air raids induced significant fear, leading to increased postwar
fertility. Conversely, the effects were negative on the northwestern side. In
this direction, air raid-related fear was likely weakest, as it faced away
from the southeast. Thus, without intense fear, bombings may have far-reaching
effects, reducing postwar fertility rates. The statistically insignificant
positive effects in other directions may result from offsetting positive and
negative impacts.

Further analysis examined far-reaching effects in the southeast and other
orientations based on damage intensity. The estimation model is as follows:

$\displaystyle\textit{CBR}_{it}=\alpha+\sum_{k=1}^{3}\beta_{sk}(C_{ki}\times\textit{Postwar}_{t}\times
I_{si})+\gamma\textit{Postwar}_{t}+\mathbf{x}^{\prime}_{it}\bm{\delta}+\nu_{i}+\varepsilon_{it}$
(4)

where $s$ denotes a directional category, indicating either southeast or
otherwise. The categorical variable $I_{si}$ specifies whether a town or
village $i$ is situated on the southeastern side of a city affected by the air
raids. Specifically, $i$ is classified as being in the southeast if it is
positioned between the south and east of at least one of the bombed cities
within 15 km. An observation $i$ that does not meet this criterion is defined
as belonging to a different directional category. Under the assumption that
only the fear of bombing differed between these directions, the difference in
the estimated coefficients is interpreted as the far-reaching effect of fear.
To ensure a sufficient number of observations in each cluster, we grouped the
damage intensity into three clusters (1–583, 855–1895, and 6,789–18,432 death
tolls).

Figure 6: Effects of bombing on fertility by damage size and direction

Notes: The dotted and solid lines indicate the point estimates and their 90%
confidence intervals, respectively. The dependent variable is the crude birth
rate (permil). The key independent variables are the dummy variables
representing each cluster of bombing damage intensity within 15 km (1–583,
855–1895, and 6,789–18,432 deaths), interacting with the postwar and southeast
dummy variables. The numbers of observations in each cluster are 133, 31, and
95 in the southeast and 196, 93, and 29 in others, respectively. The control
variables are the male-to-female sex ratio, the log of population, and a dummy
variable representing proximity to a city. The town and village fixed effects
and postwar dummy are also included. A robust standard error is clustered at
the town–village level.

Figure 6 presents the results. For towns and villages situated southeast of
the bombed cities, the estimated coefficient is negative in the cluster with
the least impact. However, a noticeable upward trend is observed, culminating
in a significant positive effect in the most intense clusters. While it is
impossible to exclude insecurity as a contributing factor to this upward
trend, these results suggest that severe air raids amplified the sense of
threat, leading to more childbirths after the war.

Conversely, non-southeastern areas consistently yield negative outcomes in all
damage clusters. This pattern implies the dominant role of insecurity or
nationalism in shaping the far-reaching effects of the bombing. Furthermore,
larger coefficients in severe damage clusters suggest fear as a significant
factor in the effect, even outside the southeast. Even in the cluster with the
highest damage level, the increase in effect size was minor. Hence, fear
intensity and its impact on postwar fertility depend on direct sensory air
raid experiences. Alternatively, the slight non-southeastern increase may
result from the insecurity caused by bombings.

Although the estimated coefficients represent the cumulative effect through
various mechanisms, the difference between southeast and other directions’
coefficients highlights the pure fear effect. The differences in effects
across the damage intensity clusters exhibited a gradual increase, with values
of 1.25, 1.88, and 3.63, respectively, from the least to the most intense
clusters. This widening gap supports the high fear susceptibility in
southeastern city areas and its far-reaching positive effects on postwar
fertility.

##  5 Conclusion

This study unveils significant postwar fertility impacts from WWII air raids
in Japan’s Kinki region. Using panel data of 1935 and 1947 town- and village-
level fertility rates and air raid death tolls, we studied impacts in areas
near bombed cities, unaffected by bombings.

Through regression analysis grounded in robust historical evidence, we have
demonstrated that the bombing’s impact extended to a radius of 15 km. Intense
air raids could have positively influenced postwar fertility, whereas less
severe air raids had the opposite effect. Our simple calculations suggest that
both effects correspond to approximately 5% of the mean crude birth rate at
that time. However, our focus was limited to the 1947 effects, and aerial
bombardment may have had more pronounced impacts at different times.

Furthermore, our quasi-experimental approach suggests a fertility increase in
municipalities southeast of bombed cities, where Allied bombers likely passed
during raids. While revealing the complex mechanisms linking air raids to
indirect fertility impacts is challenging, this finding suggests that wartime
threats and fears may have contributed to a postwar birth rate increase.

The far-reaching effects in this study may differ from those of Harada et al.
(2022), who studied air raids in Tokyo and linked community-level social
capital development to direct damage. However, indirect impacts can vary based
on measures and timeframes. Hence, this study offers a new perspective on
fertility impacts, underscoring the need for broader research on air raid
repercussions.

## Acknowledgment

We would like to extend our heartfelt appreciation to the participants of the
Economics Workshop at Meiji University, CIGS Meeting, CSG Workshop at Meiji
University, and the Economics and Game Theory Seminar at Tokyo University of
Science for their valuable insights and feedback. This study received support
from a Grant-in-Aid for Early-Career Scientists [Grant Number: 22K13440] and a
Research Fellowship for Young Scientists [20J21183]. All errors or omissions
in this work are solely our responsibility.

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