An Opportunity Cost Approach to Fertility Pattern
in 19th to early 20th century Korea
Jane Yoo and Sangkuk Lee (Ajou University, Korea)
e-mails: janeyoo@ajou.ac.kr, okllsskh@ajou.ac.kr

This study explores the determinants and the pattern of a family's decision in controlling fertility froman opportunity cost perspective. Many argue that research priority should be given to the economic
attributes of the following changes to determine the extent to which they influence marriage, fertility,and investment in children. A family has motivation in bearing more children when the increase in thenumber of children increases production capacity of a family.
The value of children, however, is found not only in an economic but also in a psychological context.
More specifically, a family has strong motivation to succeed the value of a family (lineage) for a longperiod. And having a child increases opportunity costs of parents or a family. First, it is psychologicallyhard to bear children. Second, parents need to substitute their consumption expenditure with that forchildren. That is, parents tend to have more children until the marginal benefit of a child is greater thanthe marginal costs of having a child. The net costs of a child is different not only across families but
also across periods by the development of social infrastructure. In the empirical analysis, we control thefixed-time effects to consider the improvements in the technology of contraceptive goods and services
reckoned in terms of their effectiveness and their cost to the family, and the improvements and thedeclines in the price of labor-saving consumer items. The time effects also summarizes changes in theeconomic opportunities of investing in the education of children and changes in the labor-market
opportunities for women and for teen-agers as an economy develops. Additionally, this cohort-level
analysis with the time effect reflects the decline the cost of reducing infant mortality by a change thatcurrently characterizes mainly the developments underway in poor area.
We analyze two microdata - Jokbo and Jejeokbu - in 19th to early 20th century Korea. Our family-level
data are unique: we link two micro data, Jokbo and Jejeokbu for the overlapping period. Jokbo (族譜,a genealogy) has been popularly used for studying life events of individuals because it contains therecords of birth, marriage, child-delivery, and death. Although it contains the information about one

ancestral line, it includes so many individuals that analysts can consider it a part of panel data at acertain point of a tree. Jejeokbu (除籍簿, a dropout record from the registration) contains similar
information with Jokbo. We use the Jejeokbu of the same region with Jokbo. Jejeokbu complements
the weakness of Jokbo by containing people's record from a different lineage or a different social status
to complete cross-sectional data. By connecting each year's individual data with those of other years,
we generate the time-series cross-sectional data that contain more than 30,000 individuals, born
between 1800 and 1940s. We assume that taste toward fertility is fixed for all by the restriction on theregion and the period in which individuals lived.
We first examine the trend of the age-specific mortality rate during this period and then move our focus
to the fertility pattern. We summarize the mortality patterns according to our robust Ordinary Least
Squares (OLS, henceforth). In order to improve our understanding on the factors in increasing the lengthof a life for the period, we examine factors by survival analysis and hazard ratio. We use cross-sectional
OLS and Logit model to find the determinants for a family to have more or less children. Next, wehighlight what the major factors that make a family have more children using information about social
status, household location, and parents' health conditions. We also consider changes in a social
environment - such as a colonial period and the development of health care technologies - in analyzing
the statistical significance of variables' marginal effects. Additionally, we analyze factors that influenceon the number of sons and daughters to study if there was a male-oriented rule in allocating resources
and keeping its lineage.
Some noteworthy findings are i) when a family lives in an urban area or close to a city, it is highly likely
to have more children; ii) with a lower social status of a father, the family tends to have less children;iii) if a father or a mother was born between 1800 and 1940s, they closer to 1940s tend to have fewer
number of children, sons in particular; iv) it is not statistically significant for the first son to have active
fertility control in giving birth of son.