My dissertation examines the role of horizontal stratification (qualitative differences within the same education level) in higher education for social stratification and inequality. Sociological studies, that have long debated the role of educational expansion for social mobility, have often assumed that increased access to higher education occurs uniformly. However, the limited focus on the quantitative increase in the number of highly educated individuals may obscure another important mechanism, that is, the growth of institutional heterogeneity through the proliferation of lower-tier institutions. This study examines the case of status attainment, and two critically related outcomes – assortative mating and gender stratification.

Chapter 1

Title: Horizontal Educational Stratification through a Genetic Lens: Effects of Social Background and Genetic Endowment on College Selectivity and Wages (in preparation for submission)

In this chapter, I examine the role of horizontal stratification for social mobility with a genetic lens. Specifically, I take advantage of molecular-level genetic data, that help to measure at least part of the ability endowment, to provide insights into how such biological endowments from parents are associated with social origins, access to selective colleges, and how these interactively contribute to the labor market outcomes.

Chapter 2

Title: Explaining Declining Trends in Educational Homogamy: The Role of Institutional Changes in Higher Education in Japan (in-press at Demography)

In this chapter, I examine the role of horizontal stratification for explaining educational assortative mating trends. Specifically, I examine whether the bifurcation between high- and low-tier institutions in the context of high participation in tertiary education may help us understand the mixed evidence on educational homogamy trends across countries.

Chapter 3

Title: Exam Retaking as a Source of Gender Stratification: The Case of Female Underrepresentation in Selective Colleges in Japan (work in progress)

In this chapter, I examine how the seemingly fair meritocratic selection based on test scores in transition from upper-secondary to higher education contributes to the persistence of women’s “leaky pipeline” to selective colleges by treating men and women with a similar academic aspiration and competitiveness differently.