Heterogeneous Fertility Behavior among Highly
Educated Women in Japan:
The Effect of Educational Assortative Mating on First andSecond Childbirth Using Diagonal Reference Model *Fumiya Uchikoshi(The University of Tokyo)
Abstract
Prior studies have argued that changes in nuptial behavior are the main contributors to thedecline in fertility in Japan and educational gradients in fertility are negligible. Recently,
however, changes in marital fertility have also contributed to the decline in fertility. Wh ile theinfluence of women's educational attainment on fertility has only been paid attention, sincefertility involves two partners and so it is also possible focus on the influence of the malepartner’s social status. Moreover, not only can each partner’s socioeconomic status, but also
their combining as a couple (assortative mating), influence fertility. In spite of theoreticalsignificance to examine the relationship between educational assortative mating and fertility,
scholars face a methodological problem in examining an interaction of two variables. In thisstudy, applying diagonal reference model to event history analysis, I estimate the effect ofeducational assortative mating on having first and second childbirth in Japan. A series ofanalysis reveals that homogamy couples of the high educated are less likely to have their second
child than other types of educational coupling.
Keywords: fertility, educational assortative mating, Japan

1. Introduction
Prior studies have argued that changes in nuptial behavior are the main contributors to
the decline in fertility in Japan (Iwasawa 2002). Some scholars, for example, havesuggested that educational gradients in fertility are negligible, after controlling for
demographic factors such as age at marriage (Fukuda 2005; Shirahase 2000; Youm andYamaguchi 2016).
*

The study was supported by JSPS KAKENHI Grant Number JP25000001.
1―77―

Recently, however, changes in marital fertility have also contributed to thedecline in fertility (Hiroshima 2001; Kaneko 2004). In particular, the effects ofwomen’s education (Rindfuss et al. 1996), or labor force participation (Brewster andRindfuss 2000), on fertility have been examined. For this reason, an analysis of fertility
differentials, depending on social status, is worth examining in Japan, which is known
as one of the lowest low-fertility countries (with a total fertility rate of 1.45 in 2015).
Consequently, for this study, I examined the role women’s education plays infertility outcomes in Japan. Theories of New Home Economics predict that women’s
improved access to higher education and the labor market accompanies an increasing
number of highly-educated women, who have a larger opportunity cost when balancing a
combination of family and work (Tsuya and Mason 1995). Therefore, women’s higher
education is expected to be associated with lower fertility. On the other hand, therelationship between women’s education and earning potential is ‘loose’ in East Asiansocieties, including Japan, because the gender division of labor, both in public andprivate spheres, has been persistent (Brinton and Lee, 2001: 134). Rather, in Japan,
highly-educated women’s non-participation in the labor market could be justified throughinvesting in their children’s education, based on the accumulated human capital (Yu2009: 113), where the role of a mother’s education has often been emphasized (Hirao
2001).
As stated, the assumptions made by scholars concerning women’s education
seem to be confused. In some studies, women’s higher education is associated with low
fertility because of its linkage to larger opportunity costs, while other studies assume thisis merely conjecture in the case of Japan. This theoretical discrepancy among scholars
partly stems from the difficulty in assessing women’s human capital, or gauging theirpreference for a work/family balance, directly based on their educational attainment. To
solve this methodological problem, in this study, I propose that the heterogeneity ofwomen’s education could be identified through focusing on their partner’s status.
Theories of mate selection argue that the role of preference matters in the formation of
spouse-paring patterns (Kalmijn 1998); while marrying a highly-educated man is partly a
result of the woman’s preference for hypergamy, among those who expect a husband tofulfill an earning role in the household, their preference for marrying a lower-educated
man is associated with the woman’s lower expectations of the husband’s earningpotential. Thus, looking at the spouse’s status, and a combination of the wife’s andhusband’s status, could contribute to understanding highly-educated women’s different
2―78―pathways to fertility outcomes.
In this study, I tested a series of hypotheses to predict the fertility ofhighly-educated women in Japan, using a Social Stratification and Mobility (SSM)
dataset. This paper is divided into five sections. In the second and third sections, I review
past studies on the relationship between education and fertility, and explain threepossible hypotheses regarding the impact of the patterns of the wife’s and husband’s
educational attainment, i.e., educational assortative mating on childbearing. The fourth
section presents the methods and data used. The results are reported in the fifth section.
The discussion, future developments, and conclusions are presented in the final section.

2. Literature review
2.1 Women’s economic independence and the decline in fertility
In most developed countries, the total fertility rate (TFR) has declined to below the
replacement level. Theories on the relationship between socioeconomic status andfertility have emphasized women’s better access to higher education, and the increase in
their earning potential. One hypothesis, proposed by Becker (1973) and other scholars instudies of New Home Economics, emphasizes the role of specialization by gender, andwomen’s economic independence through completing higher education. In Becker’s(1973) theory, male candidates in the marriage market were seeking women to fulfill ahousekeeping role, while women were seeking a male partner with earning potential(Becker 1991).
In this situation, gender-specific roles are important in the decision to form a
relationship, rather than staying single, because men and women together have more togain through marriage, involving a relative advantage in the household for women, andthe same in the labor market for men. In hypothesizing a marital formation as such,
scholars in New Home Economics have predicted that women’s improved access tohigher education and the labor market accompanies an increasing number ofhighly-educated women for whom there is a larger opportunity cost in balancing a
combination of family and work (Tsuya and Mason 1995). Therefore, this hypothesis
predicts that highly-educated women marry less, and are less likely to have children.

2.2 The intensive role of women on children’s education in JapanThe hypothesis that there is a strong link between women’s better access to higher
education and their increased earning potential might be mere conjectural. In particular,
3―79―as Brinton and Lee (2001) argued, women's better access to higher education is loosely
associated with labor force participation in Japan. Rather, mothers are strongly expected
to play the role of good teachers at home, so as to produce highly-educated children(Brinton 1993; Hirao 2001; Tsuya and Choe 2004), and thus investing in the child’s
education in this way could “justify highly educated women’s inability to utilize their
human capital in the workplace” (Wu 2009: 113).
Empirical literature supports the association between women’s education andtheir involvement in their children’s education. Both the father’s and mother’s education
contribute to their financial investment in their child’s private education, and in theirattitudes to childrearing (Shirahase 2011, 2012). Also, women’s participation in the labor
force is negatively associated with children’s enrollment in after-school ‘cramming
schools’ (juku) (Hirao 2007), and women’s educational attainment is positively
associated with the mother’s involvement in their child’s education (Holloway et al.
2008), and their participation in preschool (Yamamoto et al. 2006) and afterschool(Tsuya and Choe 2004) programs. In Japan, the expected higher expenditure on
education is often cited as the gap between the desirable and projected num ber ofchildren (National Institute of Population and Social Security Research 2012). A theoryof quantity and quality of children (Yamaguchi 2009) hypothesizes that the highly
educated are more likely to emphasize the quality aspect of their children, and restrict
quantity.

2.3 Educational assortative mating and its relation to fertility
The decline in TFR rate in the developed nations has an aspect as being a process of
reducing the differential fertility among the social classes. While in the past , scholars
have examined the relationship between social mobility and differential fertility (Berent
1952; Duncan 1966), the influence of women's educational attainment on fertility has
only been paid attention in recent years, possibly because of the relative improvement in
women's access to higher education.
Fertility involves two partners, however, so we can also focus on the influence ofthe male partner’s social status (Corjin et al. 1996). For women, if marriage acts as anopportunity for social mobility, it is decisive to consider the influence on fertility of not
only the woman’s, but also the male’s educational attainment (Huinink 1995). Moreover,
not only can each partner’s socioeconomic status, but also their combining as a couple(assortative mating), influence fertility (Dribe and Stanfors 2010). In the economic
4―80―

model of division of labor, male candidates in the marriage market seek women who willtake up a housekeeping role, and women seek male partners with earning potential tosupport the home (Becker 1991). Therefore, it can be predicted that the fertility of a
hypergamous couple (where the status of the female is lower than that of the man) is
higher than in other types of couples. Alternatively, since homogamous couples are
predicted to have similar values, and are less likely to divorce (Tzeng 1992), the fertilityof homogamous couples is potentially higher than for heterogamous couples.
Predicting a similar result through a different mechanism, scholars indemography have paid more attention to the increase in hypogamous couples in recent
years. Due to women’s better access to higher education over the decades, more womenthan men are involved in higher education in most of the developed nations (DiPrete andBuchmann 2013; Esteve et al. 2016; van Bavel 2012). Esteve et al. (2016) determinedthat the proportion of female college graduates aged 25 to 29 years was higher than formales in 139 countries in 2010. While female hypergamy was the normative type ofunion in the past, this structural change in higher education has decreased the proportionof hypergamous couples (Esteve et al. 2016).
Because of changes in the assortative mating trend, hypogamous couples, whowere considered to be non-normative, have declined relatively due to its disadvantages(e.g., the high risk of divorce) in the United States (Schwartz and Han 2014). In
European countries, on the other hand, the number of female breadwinners has increased,
and hypogamous couples are predicted to divide labor differently between the wives andhusbands. Based on the increase in the number of hypogamous couples in developed
nations, the consequences of educational hypogamy has been intensively examined.
Nomes and van Bavel (2016) hypothesized that an increase in educational
hypogamy in Belgium has contributed to a decline in fertility over several decades. They
provided three causal mechanisms to hypothesize that hypogamic unions are negatively
associated with fertility. First, the opportunity cost of childbearing could be considerablyhigh in households where women out-earn their husbands. Secondly, there aredifferentials in marital timing between lower- and higher-educated people. Consequently,
women in hypogamic unions tend to postpone their fertility behaviors. Third, women’s
preferences concerning the number of children they will have might be associated withexpected spousal pairings; women who want to have more children might need to rely on
the husband’s earning potential, while highly-educated women who do not want to havechildren may selectively choose partners whose status is lower than theirs. Therefore,
5―81―

women in hypogamic unions are assumed to have fewer children compared to women inother types of assortative mating.

2.4 Methodological challenges estimating the effects of assortative
matingIn spite of the efforts of previous studies to accumulate knowledge concerning how
education, and its relations, affect fertility, a methodological problem occurs in
examining a combination of (more than) two variables (i.e., an interaction effect).
Eeckhaut et al. (2013) divided standard approaches to the interaction effects of a couple’s
education levels into two groups. One is the absolute difference approach, which treats
educational coupling as a continuous difference in years of schooling between wives andhusbands. The other is the categorical difference approach. As its names suggests, theapproach categorizes couples’ educational patterns into several types, usually homogamy,
hypergamy, and hypogamy.
Both approaches have advantages and disadvantages. The former is useful interms of using fewer degrees of freedom, and an easier interpretation of the coefficients,
while it is often criticized for ignoring the qualitative differences for each education level.
The latter focuses on the categorical aspects of educational attainment, but it sometimes
omits the main effects of educational attainment. Even when including the wife’s andhusband’s educational attainment, in addition to the combination variables, it is difficult
to interpret what the coefficients mean.
An alternative approach––the diagonal reference model––was proposed by Sobel(1981). The method is characterized as measuring the effects of educational couplingfrom a weighted average of two diagonal cells. While Sobel (1981) used this model toestimate the effects of mobility on fertility, this model is also applicable to the case ofassortative mating. In spite of the theoretical significance of examining the relationshipbetween educational assortative mating and fertility, this innovative method has not been
applied in prior studies. Therefore, this study compares different approaches tomeasuring the effects of educational assortative mating.

3. Current study and hypothesis
How does educational assortative mating influence fertility in Japan? This is worth
examining because a focus on household combination, in addition to the wife’s andhusband’s educational attainment, could contribute to the understanding of the
6―82―heterogeneous effects of women’s higher education on fertility, and whether marrying ahighly-educated man or not is partly associated with women’s preferences concerning
subsequent life trajectories. In terms of the motivation behind this study, marrying ahighly-educated man indicates a woman’s relative preference towards relying on thehusband’s earning potential. Since marrying a highly-educated man, often with relatively
stable employment, and a higher income, decreases the women’s labor force participation(Shirahase 2007), women are more likely to invest in their children’s education thanthose highly-educated women who married a lesser-educated man. Therefore, I propose aseries of hypotheses to test the relationship between educational assortative mating
among highly-educated women and their fertility outcomes.
On the one hand, if we follow the argument of Nomes and van Bavel (2016),
which examined the impact of educational assortative mating on childbirth in Belgium,
women in a hypogamous couple are more likely to be the out-earner in the household
than are women in other types of educational assortative mating (Hypothesis 1a). Also,
regardless of the order of childbirth (first and second birth) hypogamous couples are lesslikely to have children (Hypothesis 1b).
On the other hand, if we focus on the cultural expectation towards women, andthe theory concerning the price to women of childbearing, homogamous men and women
who are both highly-educated are more likely to invest in their children’s education,
while educationally hypogamous couples are less likely to spend on their children’s
education (Hypothesis 2a). Also, homogamous men and women who are both
highly-educated are less likely to have a second child, while the likelihood of having afirst child does not depend on educational assortative mating (Hypothesis 2b).

4. Data and methods
The data used in this study is from a series of the SSM surveys from 1985 to 2015 (seehttp://www.l.u-tokyo.ac.jp/2015SSM-PJ/ for details). This cross-sectional survey consistsof a multistage, nationally-representative, and randomly-sampled, population in Japan.
This data was chosen because it captures detailed retrospective family and occupational
histories, and covers a wide range of individuals, which allows an examination of thelong-term relationship between education and fertility.
I use different samples to test each hypothesis. First, the SSM surveys from 1985,
1995, 2005, and 2015 were used in examining the relationship between educational
assortaitive mating and wife’s income share. Second, the SSM survey of 2005 and 20157―83―

were used to examine whether an expenditure on children’s education differs byeducational assortative mating. Questions about educational spending started to be asked
from the SSM 2005. Third, the SSM from 2015 was used to test the main question in thisstudy: the relationship between educational assortative mating and childbearing. I use
only the SSM 2015 for testing the last question because this survey asked questions
pertaining to not only current marriage, but also respondents’ first marriage, if they weredivorced, widowed, or remarried. Therefore, this study was able to examine, and focus
on, the first marriage and its fertility.
The main independent variables are the wife’s educational attainment, husband’s
educational attainment, and their combination. Educational attainment is categorized into
four groups (i.e., junior highschool, highschool, junior college, and university andhigher). Therefore, the compound variables of a couple’s educational attainments provide
15 (16-1) coefficients to the maximum. As for types of educational assortative mating, inaddition to the hypergamy or hypogamy of the couples, I divided homogamous couples
into two types: homogamy of the highly-educated (wives and husbands are either bothjunior college graduates, or university graduates) and homogamy of the lesser-educated(wives and husbands are either both highschool graduates, or junior highschool
graduates).
In examining the effects of educational assortative mating on childbearing, I
created a person-year database of female respondents, which starts from the year of thefirst marriage to estimate the first birth, and the year of the first birth to estimate thesecond birth. In addition to the null model that includes variables of educational
assortative mating, I also present the results of a full model that controlled covariates
such as age at marriage, marital cohort, age at first birth (only for the second birthsample), respondent's employment status (t-1), and whether the respondent is divorced or
not (t-1).
The equation of diagonal reference model is as follows. In this model,
dependent variable Yijk is defined as a weighted parameter of distance from averagevalue of μii and μjj, which are located as diagonal cells of each educational attainment. It
is possible to add covariates (x ijk) to this model.

Distribution of the variables used in this study are shown in Table 1 and 2. In
8―84―

Table 1, I present the distribution of variables used in the first and second analysis(wife’s income share and expenditure on education) and in Table 2, I present the
distribution of variables used in the third analysis (childbearing).
Table 1. Descriptive statistics (wife's income share and educational expenditure)

Table 2. Descriptive statistics (childbirth risk)

9

―85―

5. Results
5.1 The relationship between educational hypogamy and wife’s income
sharePrior studies have assumed that educational assortative mating is associated with acouple’s balance of power. Specifically, among couples in which women are moreeducated than their husbands, it is more likely that these women out-earn their husbands,
and so have a relative advantage in decision-making processes in the household. The
relationship between women’s educational hypogamy and their relative advantage inearnings has not been tested in the Japanese context, however. A particularly important
aspect of women’s labor in Japan is that Japanese women tend to quit work after
marriage or childbearing, regardless of their educational attainment, which is a proxy foraccumulated human capital (Brinton and Lee 2001). It is also likely that there is aheterogeneity among highly-educated women, in terms of their labor force participation
depending on whether their spouse is also highly educated or not.
Therefore, to test this conjecture concerning such relationships, I examined
whether (highly-educated) wives that tended to out-earn their husbands were associatedwith their partner’s status (whether the husbands were also highly educated or not). Afterexcluding cases with missing data on variables used in this analysis, I ultimately used
4853 cases in the SSM surveys (married women aged 20 to 60 years at the time of theinterview).
The definition of a female out-earning couple is as follows. The SSM surveys
measured annual income between respondents and their spouses separately, but it ismeasured by binned scale. Therefore, about 5% (254/4853) of couples were categorized
as equal-breadwinner. To distinguish equal-breadwinner couples from female out-earning
couples, this study defines female out-earning couples as couples in which the wife earns
more than 50% of the husband and wife’s joint income.
Table 3 presents the result of regression. I included control variables (i.e., survey
year dummies, age, age of the youngest child, and spouse’s non-employed dummy).
Compared with the homogamy of the highly educated, hypogamy, in which the wife’s
education is higher than that of the husband, is more likely to be a female out-earning
couple, and the relationship is statistically significant at the 5% level. In contrast,
homogamy of the lesser educated, and female hypergamy couples, are slightly more
likely to be female out-earning, but this is not statistically significant. These results
suggest that women in a hypogamy couple particularly tend to out-earn their husbands,
10

―86―

and the spouse’s educational attainment matters, not only the wife’s educational
attainment, in determining whether the household tends to be female out-earning.
Table 3. Determinants of wife's income share and expenditure on children's education

That said, this regression does not include the wife’s and husband’s specificeducational attainments as independent variables. Therefore, I examined the relationshipusing a DRM model in Table 4. This model includes the wife’s and husband’s
educational attainments as average values of μii and μjj, which are located as diagonalcells. This model also supports that educational hypogamy is positively related to female
out-earning at the 5% level, and the positive effect of educational hypogamy on female
out-earning is slightly higher in the DRM model than in the normal logistic regression
model.

11―87―

Table 4. Determinants of wife's income share and expenditure on children's education(DRM)

5.2 Do highly educated couples spend more on their children’s
education?
The next research question tested in this study was the relationship between educational
assortative mating and the household’s expenditure on the children’s education. The
dependent variable used in this analysis was monthly financial expenditure on the
12

―88―

children’s education outside of school. Since this variable does not measure educational
spending for each child, I included the number of children in the statistical model. Since
this variable by nature was asked to respondents who have a child, the sample in thisanalysis is limited to marriage women who are aged 20 to 60 years at the time of theinterview and have at least one child (1074 cases).
I hypothesized that, among the highly educated, women who married a man
whose educational attainment was lower than hers (i.e., educational hypogamy) were lesslikely to spend on their children’s education than women who married a man with thesame level of higher education because it is predicted that, if women are interested inraising a high-quality child, in terms of their educational attainment, it matters that she
has a highly-educated man as a spouse.
Table 3 presents the result of the regression. Since the expenditure on education
for children was not normally distributed, I used the logged value as a dependent variable.
In addition to the main independent variables, I included a survey year dummy, age andage squared, and the respondent’s and spouse’s annual income. Compared to thehomogamy of the highly educated, hypogamous couples are less likely to spend on theirchildren’s education, while it is the homogamy of the lesser-educated couples that areleast likely to spend on their children’s education. To add, the effect of hypergamy on
expenditure on children’s education is much the same as that of highly educatedhomogamous couples.
To further examine the relationship between educational assortative mating andeducational expenditure, Table 4 presents the results of the DRM models. Since adding
multiple dummy variables of educational assortative mating does not allow the mode l toconverge, I included each dummy variable separately. The results show that educational
hypergamy couples are more likely to spend on their children’s education than othertypes of couples. Also, hypogamous couples are less likely to spend on their children’s
education, which supports the hypothesis of this study.

5.3 Educational assortative mating and fertility differential
5.3.1 Descriptive results
Results of the analysis above indicated that wives in hypogamous couples were more
likely to out-earn their husbands, while the educational expenditure on their children’s
education outside of school was below average among educational hypogamy couples. In
contrast, homogamy of the high educated couples are more likely to spend their money
13

―89―

on investing in their children’s education.
In this section, based on the results of analysis, I examine whether educational
assortative mating matters for first and second childbirth risks. On one hand, Hypothesis
1b predicts that, since educational hypogamy couples tend to be female out-earning, theirchildbirth risk is lower than for other couples, regardless of first and second childbearing.
On the other hand, hypothesis 2b, derived from theories of quantity/quality of children,
predicts that it is homogamy of the highly educated who are more likely to restrict their
number of children. This does not mean, however, that these highly-educatedhomogamous couples are less likely to have their first child because the gist of the theoryis that these couples restrict their number of children in order to invest more in thequality of the children, in terms of their education.
I first estimated the descriptive survival rates of having a first and second child,depending on the types of educational assortative mating. Since homogamous couples
include both the lesser and highly educated, I separated this type of pairing into lesser(junior high and high school) and highly- (vocational/junior colleges and university)
educated groups.
Figure 1 shows the survival function of first birth among these four educationalgroups. Homogamy of lesser-educated couples are the most likely to have their firstchildbirth during the first half of the survival time, and the hypogamous couple follows.
Homogamy of highly-educated couples are less likely to have their a child, but the gap intheir propensity to bear a child gradually decreased and, during the second half of thesurvival time, the propensity of the homogamy of highly-educated couples to bear child
was almost the same as in the other groups. Not surprisingly, these differentials in
fertility timing occur because lesser-educated couples tend to marry earlier. Therefore,
we need to examine whether educational hypogamy couples are more likely to have achild compared with other groups, by controlling the demographic covariates.
Figure 2 shows the survival functions of second childbirth among those groups.
Compared with the survival function of first birth, in which more than 90% of the
population experienced their first birth, the probability of couples having a second childis slightly lower. It also demonstrates that homogamy of highly-educated couples are lesslikely to have a second child than other couples; however, a similar problem occurs as we
factor in the survival function of first birth. In this case, it is highly likely that hypergamyof highly-educated couples have their first child later than other couples. Therefore, weneed to control not only the timing of marriage, but also the timing of first child birth in
14

―90―

estimating the propensity to have second child birth, and its differentials among the four
educational groups.

Figure 1 Survival curve of first childbearing

Figure 2 Survival curve of second childbearing
15

―91―

5.3.2 Multivariate results
Table 5 shows the results of a discrete time logistic regression, which predicts thelikelihood to have first and second child. Models in this table include only combinationsof the wife’s and husband’s educational attainments (assortative mating). While results of
the null model show that, compared with homogamy of the highly educated, other typesof couples are more likely to have first and second child, this relationship is partly
cancelled out by including control variables, such as age at marriage or age at first birth.
Model 2 for both the first and second births suggests that hypogamy couples are
particularly more likely to have the child than homogamy of the highly educated.
Table 5. Determinants of first and second childbirth

These models, however, did not consider the baseline effects of each wife’s andhusband’s educational attainments. To precisely capture the effect of a couple’s
16

―92―

educational pattern on fertility differentials, I examined diagonal reference models in
Table 6, which shows a contrasting result between the first and second childbirth. In thefirst birth regressions, there is no significant difference between the four types of
educational assortative mating, regardless of including control variables or not. In thesecond birth mode, in contrast, it is the homogamy of the high educated that are least
likely to have the second child, although the full model suggests that its likelihood tohave the second child is not significantly different from the hypergamy couples. These
results suggest that a fertility differential is observed in the second childbearing, rather
than the first childbearing, and highly-educated homogamous couples are less likely tohave a second child, but they are equally likely to bear the first child, compared withother types of couples.
Table 6. Determinants of first and second childbirth (DRM)

17

―93―

6. Discussion
In this study, I examined the relationship between educational assortative mating andfertility outcomes in Japan. Theories on how and why women’s educational attainment
matters for their fertility are divided among several camps. In particular, women’s
increasing opportunity cost to balance family and work might not be applicable to theJapanese context. Rather, these highly-educated women find it difficult to continue intheir occupational careers, but they can justify their educational attainment throughraising a high-quality child, in terms of the child’s educational attainment. For thosehighly-educated women, rather than selecting to be childless, it is more rational to limit
the number of children. Therefore, while the opportunity cost hypothesis predicts thathighly-educated women are less likely to have a child, the quality/quantity hypothesis
predicts that these women are likely to have a first child, but less likely to have a second
child.
Since the diagonal reference model is the most parsimonious and best fit model for
estimating the effect of educational assortative mating on fertility differentials (Eeckhaut
et al. 2013), I used this model to examine the relationship between educational
assortative mating and couples’ different preferences towards the earnings role,
expenditure on children’s education, and childbearing. The results show that homogamyof the highly-educated couples are more likely to spend on their children’s education
outside of school, while they are less likely to bear a second child than other types ofcouples, as the quality/quantity hypothesis predicted. In contrast, although it is the casethat wives of educational hypogamy couples tend to out-earn their husbands, comparedto wives of other educational assortative mating couples, these hypogamy couples are notless likely to bear a first and second child, compared to highly-educated homogamous
couples. Therefore, the results of this analysis support the quality/quantity hypothesis.
This is an understandable result in the Japanese context. Japan is known for its
poor public expenditure on education, and thus private sectors (households) play a majorrole in education expenditure among OECD countries. Possibly due to this structure,highly-educated couples tend to have fewer children, so as to be able to invest more in
the child’s education, than lesser-educated couples (Shirahase 2011, 2012). In addition,
women’s better access to higher education is loosely related to labor force participation.
Therefore, if highly-educated women marry highly-educated spouses, their motivation tocontinue in their career is expected to be lower, compared to those highly-educatedwomen who marry down (i.e., marry a lesser-educated husband). Although this reasoning
18

―94―

is supported from the results of regression in Tables 3 and 4, in which educational
hypogamy couples are more likely to be female out-earning compared to the homogamyof the highly educated, educational hypogamy couples do not necessarily restrict their
number of children.
This study leaves an implication to disentangling the decline in TFR in Japan.
While the main factor to decline in TFR has been the changes of nuptiality behavior inJapan (Iwasawa 2002), the decline in marital fertility started contributing to the decline
in TFR (Hiroshima 2001; Kaneko 2004). In contrast to to the Belgium case (Nomes andvan Bavel 2016), the results present that hypogamy couples do not necessarily havestatistically significant difference from the other type of assortative mating couples interms of their childbirth risk, while homogamy couples of the both highly educated havelower probability to have second birth. This means that recent decline in marital fertility
may be caused by highly educated homogamous couples. Future studies are needed toelucidate the detailed mechanism between female breadwinning couples and their family
formation, including childbearing outcomes.

Reference
Becker, G. S. 1973. “A Theory of Marriage: Part I.” The Journal of Political Economy
81(4):813–46.
――――. 1991. A Treatise on the Family. Cambridge, MA: Harvard University Press.
Berent, J. 1952. “Fertility and Social Mobility.” Population Studies 5(3):244–60.
Brewster, K., and R. Rindfuss. 2001. “Fertility and Women's Employment inIndustrialized Nation.” Annual Review of Sociology, 26, 271–96.
Brinton, M. C. 1993. Women and the Economic Miracle: Gender and Work in Postwar
Japan. California, CA: University of California Press.
Brinton, M. C. and S. Lee, 2001, “Women's Education and the Labor Market in Japan andSouth Korea,” M. C. Brinton ed., Women's Working Lives in East Asia, 125-150.
Stanford, CA: Stanford University Press.
Corijn, M., A. C. Liefbroer, and J. de Jong Gierveld. 1996. “It Takes Two to Tango,
Doesn't It?: The Influence of Couple Characteristics on the Timing of the Birth of
the First Child.” Journal of Marriage and the Family 58(1):117–26.
DiPrete, T. A. and C. Buchmann. 2013. The Rise of Women: The Growing Gender Gap in
Education and What It Means for American Schools. New York, NY: Russell Sage
Foundation.
19

―95―

Dribe, M. and M. Stanfors. 2010. “Family Life in Power Couples: Continued
Childbearing and Union Stability Among the Educational Elite in Sweden,
1991-2005.” Demographic Research 23:847–78.
Duncan, O. D. 1966. “Methodological Issues in the Analysis of Social Mobility.” In N. J.
Smelser and S. M. Lipset (eds.) Social Structure and Mobility in Economic
Development, 51–97. Chicago, IL: Aldine Publishing Company.
Eeckhaut, M. C. W., B. Van de Putte, J. R. M. Gerris, and A. A. Vermulst. 2013.
“AnalysingtheEffectof

Methodological/Theoretical

Educational

Differences

Comparison.”

European

BetweenPartners:

Sociologicala

Review

29(1):60–73.
Esteve, A, C. R. Schwartz, J. van Bavel., I. Permanyer, M. Klesment, and J.
García-Román. 2016. “The End of Hypergamy: Global Trends and Implications.”
Population and Development Review 42(4): 615–25.
Holloway, S.D., Yamamoto, Y., Suzuki, S., and Mindnich, J.D. 2008. “Determinants of
Parental Involvement in Early Schooling: Evidence from Japan.” Early Childhood
Research and Practice, 10(1).
Hirao, K. 2001. “Mothers as the Best Teachers: Japanese Motherhood and Early
Childhood Education.” In Mary C. Brinton (ed.) Women's Working Lives in East
Asia, 180-203. Stanford, CA: Stanford University Press.
――――. 2007. “The Privatized Education Market and Maternal Employment in Japan.”
In F. M. Rosenbluth (ed.) The Political Economy of Japan's Low Fertility, 170–200.
Stanford, CA: Stanford University Press.
Hiroshima, K. 2001. Shusshou ritu teika wo donoyou ni toraeruka? Nenreibetsu
yuuhaiguu shussyouritu no monndaisei [How to Analyze Fertility Decline?:
Drawback in Age-specific Marital Fertility Rate], Riron to Hoho [Theory andMethods], 16(2) 163-183. (in Japanese)
Huinink, J. 1995. “Education, Work, and Family Patterns of Men: the Case of West
Germany.” In H.-P. Blossfeld and J. Huinink (eds.) The New Role of Women: Family
Formation In Modern Societies, 247–62. Boulder, CO: Westview Press.
Iwasawa, M. 2002. Kin'nen-no Kikan TFR hendo-ni okeru kekkonkodo oyobi fufu no
shusshokodo no henka no kiyo-nitsuite [On the Contribution of the Changes in First
Marriage Behaviors and Couples: Reproductive Behaviors to the Recent Change inJapan’s Total Fertility Rate]. Journal of Population Problems, 58(3) 14-44. (inJapanese)20―96―Kalmijn, M. 1998. “Intermarriage and Homogamy: Causes, Patterns, Trends.” Annual
Review of Sociology 395–421.
Kaneko, R. 2004. “Shoshika katei ni okeru fufu shusseiryoku teika to bankonka,
kogakurekika, oyobi shussei kodo no sokutei [Decline in the Fertility Rate among
Married Couples, the Delay in Marriage, the Increased Level of Education, and the
Measurement of Fertility Behavior].” Journal of Population Problems 60: 37–54. (inJapanese)
National Institute of Population and Social Security Research. 2012. Marriage Process
and Fertility of Japanese Married Couples: Overview of the Results of the
Fourteenth Japanese National Fertility Survey in 2010. Tokyo: National Institute ofPopulation and Social Security Research.
Nomes, E. and J. van Bavel. 2016. “Marital Fertility and Educational Assortative Mating
Before, During, and After the Baby Boom in Belgium.” Annales de démographie
historique 132(2):139–163.
Rindfuss, Ronald R., S. P. Morgan, and K. Offutt. 1996. “Education and the Changing
Age Pattern of American Fertility: 1963-1989.” Demography 33(3): 277–90.
Schwartz, C. R. and H. Han 2014. “The Reversal of the Gender Gap in Education and
Trends in Marital Dissolution.” American Sociological Review 79(4): 605–29.
Shirahase, S. 2000. “Women's Increased Higher Education and the Declining Fertility
Rate in Japan.” Review of Population and Social Policy, 9, 47–63.
――――. 2007. “Women’s Economic Status and Fertility: Japan in Cross-National
Perspective.” In F. M. Rosenbluth (ed.) The Political Economy of Japan's Low
Fertility, 37–59. Stanford, CA: Stanford University Press.
――――. 2011. “Syoshika Syakai no Kaisou Kozou: Kaiso Ketsugo toshite no Kekkon
ni Chakumoku shite (Stratification Structure in the Age of Declining Birth Rate:
With a Focus on Marriage as Assortative Mating).” In H. Ishida, H. Kondo, and K.
Nakao (eds.) Gendai no Kaiso Syakai 2: Kaisou to Ido no Kouzou [Contemporary
Stratified Society 2: Structure of Inequality and Mobility], 317–33. Tokyo:
University of Tokyo Press.
――――. 2012. “Marriage as an Assocition of Social Classes in a Low Fertility Rate
Society.” In H. Ishida and D. H. Slater (eds.) Social Class in Contemporary Japan:
Structures, Sorting, and Strategies, 57–83. Oxon: Routledge.
Sobel, M. E. 1981. “Diagonal Mobility Models: a Substantively Motivated Class of
Designs for the Analysis of Mobility Effects.” American Sociological Review 46(6):
21

―97―

893–906.
Tzeng, J. M. 1992. “The Effects of Socioeconomic Heterogamy and Changes on Marital
Dissolution for First Marriages.” Journal of Marriage and Family 54(3): 609–19.
Tsuya, N. O. and M. K. Choe. 2004. “Investments in Children’s Education, Desired
Fertility, and Women’s Employment.” In N. O. Tsuya and L. L. Bumpass (eds.)
Marriage, Work, and Family Life in Comparative Perspective: Japan, South Korea,
and the United States, 76–94. Honolulu, HI: University of Hawaii Press.
Tsuya, N. O. and K. O. Mason. 1995. “Changing Gender Roles and Below Replacement
Fertility in Japan.” In K. O. Mason and A.-M. Jensen (eds.) Gender and Family
Change in Industrialized Countries, 139–67. Oxford, England: Clarendon Press.
van Bavel, J. 2012. “The Reversal of the Gender Gap in Education and Female
Breadwinners in Europe.” In W. Lutz, K. S. James, V. Skirbekk, and J. van Bavel(eds.) Vienna Yearbook of Population Research 10:127–54.
Yamaguchi,

K.

2009.

Work-Life

Balance:

Empirical

Evidence

andPolicyRecommendations (in Japanese). Nikkei News Publication.
Yamamoto, Y., Holloway, S. D., and S. Suzuki. 2006. “Maternal Involvement in
Preschool Children's Education in Japan: Relation to Parenting Beliefs andSocioeconomic Status.” Early Childhood Research Quarterly, 21, 332–46
Youm, Y. and K. Yamaguchi. 2016. “A Comparison of the Determinants of Low Marital
Fertility Between Korea and Japan.” Korean Journal of Sociology 50(3): 23–43.
Yu, W-H. 2009. Gendered Trajectories: Women, Work, and Social Change in Japan andTaiwan. Stanford, CA: Stanford University Press

Acknowledgments
A previous version of this article was presented at the 90th Japan Sociological Society
Annual Meeting at the University of Tokyo. The participants in the seminar and thesession provided helpful comments on the previous version of this article. I thank
Sawako Shirahase, Ryota Mugiyama (the University of Tokyo), and Ryohei Mogi (Centred’Estudis Demogràfics, Universitat Autónoma de Barcelona) for their helpful comments.

22―98―