Research

We study employment outcomes during the early stages of the COVID-19 pandemic across eight countries exhibiting different case levels and policy responses: the United States, Australia, France, Denmark, Italy, South Korea, Spain, and Sweden. While the proportion of people not-at-work increased in all countries, safety net policies seem to influence whether people remained employed-but-absent from work as opposed to becoming unemployed or leaving the labor force. We find large employment decreases among young workers and those who only have a high school degree, and increased labor market disparities in countries with the largest declines in employment. A variety of evidence suggests labor demand was a larger driver of employment declines than labor supply and that stringent social distancing policies reduce employment even in the absence of high case numbers. Job characteristics - the importance of face-to-face interactions and the ability to work remotely - were closely related to changes in labor market outcomes.

This study examines the impact of in utero exposure to ambient particulate matter (PM) on neonatal health outcomes, utilizing comprehensive population-level birth records from South Korea for pregnancies between 2016 and 2019. To address potential endogeneity concerns, the analysis adopts wind direction as an instrumental variable for prenatal PM exposure. The findings indicate that exposure to PM during the first trimester significantly increases the likelihood of preterm birth, and this effect remains robust across a range of model specifications. Moreover, the estimated impacts are consistent across different socioeconomic strata. These results highlight the critical importance of environmental health during early pregnancy and suggest that in low-fertility, late-childbearing societies such as South Korea, environmental protection efforts should be closely aligned with maternal health policies. 

I explore the causal effects of single-sex high schools on long-term labor market outcomes using a unique feature of educational policy in South Korea—the random assignment of students to single-sex versus coeducational high schools. I find that the effect of single-sex schooling on earnings is positive for women but not for men. The effect varies with job experience, increasing by 1.9 percentage points with each additional year of experience. In addition, single-sex schooling affects other labor market outcomes, including women's work hours and job satisfaction. Finally, I use measurements of completed education and job training as human capital accumulation to study potential mechanisms for gender differences in the effect of single-sex schooling.

We estimate the causal effect of ambient air pollution on early-life health and medical care utilization among children ages 0–12 in South Korea by linking National Health Insurance Service (NHIS) claims data from 2008–2018 with monitor-based pollution measures. To address endogeneity, we use a two-stage least squares strategy exploiting variation in westerly winds that transport dust and industrial emissions into Korea. Higher particulate concentrations increase pediatric respiratory morbidity and covered medical spending, with effects concentrated among children ages 0–6. Evidence from the Korea Health Panel Study (KHPS) shows no corresponding change in non-covered medical spending. Complementary evidence from the Cohort for Childhood Origin of Asthma and Allergic Diseases (COCOA) indicates that the respiratory response is primarily driven by children attending childcare facilities.

We study the fertility effects of central and local pronatalist cash transfers in South Korea. Using population-wide administrative records from the National Health Insurance Service, we exploit sharp eligibility and announcement cutoffs from the 2023 expansion of the universal Parental Allowance and estimate short-run effects using a regression-discontinuity difference-in-differences design. We find declines in births at thresholds, with larger effects among older and lower-income women, and no evidence of short-run adjustments in birth order or delivery type. Local lump-sum baby bonuses generate modest fertility gains, concentrated in non-capital areas and driven by parity-specific bonus schedules rather than broader quasi-cash benefits.

We study whether concise, policy‐linked information shifts public preferences over both the level and the rules of education finance in a setting with formula-driven earmarks. In a nationally representative online experiment of 3,066 Korean adults, respondents were randomized to a placebo control or one of three information conditions: expenditure efficiency under demographic change, international benchmarks, and cross-sector budget trade-offs. Primary outcomes map to actionable levers: the preferred central-budget share for education, the preferred share of Local Education Finance Grants (LEFG) in provincial education revenues, support for replacing a fixed 20.79\% tax linkage with student-/demand-based rules, and priorities for reallocating any surplus. Across treatments, the “appropriate” education share falls by about 2.3–2.7 percentage points; the trade-off condition raises the share labeling current spending “too high” from 25\% to 35\%. Respondents place an appropriate LEFG share near 55–57\% (vs. the current 76\%) and favor needs-based reparameterization, reallocating surplus toward child and elder care. Results show targeted facts can increase acceptance of efficiency-oriented reform without resorting to elite cues.

I estimate the effect of maternity leave on fertility in the United States, exploiting within-person variation in employer-provided leave access using individual fixed effects and NLSY97 panel data (2000-2015). Access to unpaid maternity leave raises the annual probability of childbirth by 5.4 percentage points, while the effect of paid leave is not statistically significant. The unpaid leave effect is 5.3 percentage points larger for graduate-degree women. These results are robust to controlling for job mobility, and a falsification test using lead leave access confirms the absence of anticipatory sorting. Wage regressions find no evidence of compensating differentials for paid leave, suggesting that unpaid leave operates through a job-protection channel. Mediation analysis indicates that maternity leave access explains 17.2 percent of the education-fertility gradient for college-educated women, identifying leave provision as one mechanism behind the emerging reversal of the negative education-fertility relationship.

This paper uses model selection and machine learning methods to compare methods to estimate the average treatment effect in high dimensions. I focus on regression adjustment with Lasso, approximate residual balancing, and the causal forest methods under the unconfoundedness assumption, which requires randomness of the treatment assignment conditional on pre-treatment variables. By comparing the estimation results from each method, my research can help us after which method is best for a high dimensional experiment in which minimal assumptions are satisfied. In simulation studies, the approximate residual balancing methods perform better than other methods, even in high dimensions. This paper also applies these methods to real data from Angrist and Lavy (2001). The results show that the estimates of the causal forest method are almost the same as the estimates from Angrist and Lavy (2001) in which they use an individual-fixed effect estimation.

Using data from the Korean Labor and Income Panel Study (KLIPS), this paper tests four hypotheses on the source of the marriage premium for South Korean men and women: the selection, productivity, specialization, and favoritism hypotheses. Fixed effects regression results show that men experience a significant marriage premium, while women face a significant marriage penalty, resulting in a significant gender differential in the returns to marriage. Our results are generally consistent with all four hypotheses, with the selection and favoritism hypotheses receiving stronger support than the productivity and specialization hypotheses. We conduct instrumental variable estimation throughout our analyses using the zodiac sign of the birth year to test the endogeneity of marital status, presence of children, and spouse’s labor activities, all of which are subsequently suggested not to be endogenous.

This paper investigates the enforcement effects of the “Law on the Improvement of the Mobile Terminal Distribution System (Mobile Terminal Distribution Act),” which was implemented in October 2014. Despite the nationwide attention to the legislation, an empirical analysis of the market effects of the Mobile Terminal Distribution Act is yet to be done. Using a rich dataset obtained from handset retail stores authorized by telecommunication agencies, we perform both an ordered probit MLE and a panel regression. We find the following facts. First, Mobile Terminal Distribution Act has effectively enabled consumers to choose less expensive plans. The reduced amount of subsidy for handset purchases seems to be the main reason for this phenomenon, as Mobile Terminal Distribution Act originally intended. Second, we find no statistically significant reductions in the prices of newly launched handsets. While the prices of some products have actually dropped, our analysis shows that it is not due to the implementation of the Mobile Terminal Distribution Act. 

This project examines the differential effect of school quality on academic achievements within and between school districts in South Korea. Exploiting the unique educational system and datasets of school characteristics in South Korea, I find that school quality has a positive effect on academic achievement and that its magnitude is much larger for students with low-level previous test scores. Under the random assignment system, this paper suggests that study-related facilities and additional chances to study after regular classes are important factors in improving students’ performance in addition to the traditional school quality measurements (e.g., teacher-pupil ratio and financial spending by school). Once the random assignment is relaxed, I can find a positive relationship between school quality and student background or “ability”. Though exploiting limited individual-level data, this paper supports the argument that high-quality schools attract more students (whether they have increased ability or not) and construct network formation through which the effect of school quality on academic achievements becomes stronger. 

This paper examines the long-term relationship between health expenditures, both government and private, and selected health outcomes, infant mortality, and child mortality based on the interactive fixed effects model using data from 160 countries for the years 1995, 2000, 2005, and 2010. The interactive fixed effects model allows unobservable variables like health technology to be captured by the interaction between country fixed effects and time effects. With this model, I estimate the elasticity of infant and child mortality with respect to government and private health expenditures. Results from this paper are at variance with previous studies asserting the importance of increasing public and private health expenditures on infant and child mortality. This paper also provides new evidence of the importance of taking into account the level of country-specific factors interacting with time effects for estimating more accurately the effect of health expenditure on health outcomes.