Research 

• Presentation: 2022 Missouri Valley Economic Association Conference, 2022 Michigan State University Applied Economics Seminar, 2022 Southern Economic Association Conference, Bank of Korea, Korea Labor Institute, Korea Capital Market Institute, Korea Institute for International Economic Policy, Korea Institute of Finance, Korea Institute of Public Finance, Korea Development Institute, Korea Institute for Industrial Economics and Trade, 2023 Midwest Economic Association Conference, 2023 UM-MSU-UWO Labo(u)r Day Conference, 2024 Korean Economic Review International Conference, 2024 Korea Labor Economic Association Conference, 2024 Asian and Australasian Society of Labour Economics Conference, 2025 World Congress of the Econometric Society (ESWC 2025) 

• Abstract: This paper studies the effects of minimum wages on the labor market outcomes of the elderly. In contrast to the groups that are more typically studied, I find small, positive employment effects on those in their late sixties by using a variety of methods commonly used in the literature. Point estimates of employment elasticities fall in the range of 0.1 to 0.3. The positive effects are not limited to the minimum wage workers but extend to a broader range of workers who are paid wages well above the minimum wage. To explain the results, I provide two pieces of evidence on labor-labor substitution. First, industry-level employment elasticities of the young and elderly with respect to the minimum wage are negatively correlated. Second, I directly estimate the elasticity of substitution between the young and elderly using the nested-CES production function framework. 2SLS estimates suggest that the young and elderly are substitutes for each other. Although the estimated elasticity of substitution is small, it suggests that labor demand is shifted toward older workers when minimum wages are increased. 

• Presentation: 2022 Midwest Economic Association Conference, 2023 Korea Association of Public Finance Conference, Bank of Korea Microeconomic Research Forum, 2024 Korea's Allied Economic Associations Annual Meeting, 2024 Korean Association of Applied Economics Conference 

• Abstract: This paper examines short-run adjustments of working hours to minimum wage increases. Combining longitudinal data from the matched Current Population Survey and data regarding large-scale state-level minimum wage increases, I find negative effects of minimum wage increases on working hours. Large minimum wage increases reduce working hours by approximately 50 minutes per week. These effects are neither identical nor monotonic across working hours. Workers who worked part-time or overtime prior to the increases are negatively affected in terms of their working hours, while full-time workers are largely unaffected. Adjustments are related to the 40-hour workweek. There is a large shift from overtime to 40-hour workweek positions for those working overtime in the previous year, while part-time workers are less likely to work 40 hours per week after increases. These adjustments are consistent with the predictions from a labor demand model with a kinked labor cost schedule caused by the overtime pay regulation.

• Presentation: 2021 Southern Economic Association Conference 

• Abstract: To what extent do workers earn a higher hourly wage if they work very long hours? Based on four decades of data from the Current Population Surveys and the Panel Study of Income Dynamics, our findings regarding this fundamental question about labor supply incentives are three-fold. First, the wage gap between those working very long hours (50+ hours per week) as compared to those who working a standard work week (40 hours per week) has gone from being strongly negative in 1980 to being strongly positive in 2018. Second, at the individual level, a long-hours premium currently exists for about 95% of hourly workers and 40% of salary workers within their current job because of overtime regulations, but relatively few workers earn overtime pay. Third, if were to define the individual premium to be the entire within-occupation long-hours premium, then most workers would earn an hourly wage premium by working more hours, but it is unclear whether such a broad definition is appropriate.

• Presentation: 2024 Korea Association of Public Finance Conference 

• Abstract: In the U.S., individuals in their early 60s often face limited healthcare access until they turn 65 and qualify for Medicare. This creates a clear discontinuity in coverage at age 65. Our research examines whether the 2014 Medicaid expansion reduced this discontinuity and impacted health status and utilization. Using a difference-indifferences in -discontinuity method and data from the Health and Retirement Survey (HRS) and the American Community Survey (ACS), we find that Medicaid expansion reduced the public health insurance discontinuity by 13.4% (HRS) and 10.2% (ACS). However, much of this increase was offset by crowd-out effects on private insurance, particularly non-employer plans. While there were some reductions in the discontinuity in health status and care utilization at age 65, most changes were not statistically significant.

※ Title of the previous version: Closing the Gap at the Age of 65: Evidence from the Medicaid Expansions 

• Presentation: 2024 Korea Association of Health Economics and Policy Conference*, 2025 Korea's Allied Economic Associations Annual Meeting, Korea Labor Economic Association Monthly Seminar (Mar 2025)*, Sungkyunkwan University*, Kyung Hee University* 

• Abstract: While negative externalities provide a primary rationale for heavy taxation of tobacco products, there is limited evidence on how a tobacco tax affects the incidence of passive smoking and overall welfare. This paper examines the impact of a tobacco tax hike on active and passive smoking by using cotinine, a biomarker of nicotine exposure. The tax hike reduced passive smoking and increased non-smoking in the year of implementation, although it had no statistically significant effect on active smoking. Its impact became more pronounced over the subsequent two years. To assess the welfare implications of the tobacco tax increase, we develop a sufficient statistics framework that incorporates externalities imposed on passive smokers. We estimate a threshold for the monetary costs of passive smoking, above which the tax becomes welfare-improving. These findings underscore the importance of including passive smoking in welfare evaluations of tobacco taxation.

• Presentation: Seoul Labor Economics Working Group (LEWG), Bun Song Lee Population and Aging Lab, 2025 Korea Labor Economic Association Conference, Yonsei University 

• Abstract: This paper examines the relationship between minimum wage increases and the distribution of working hours using the 2018–2019 minimum wage hikes, with a focus on the growth in the share of workers working fewer than 60 hours per month in South Korea. Institutional features generate a substantial notch in labor costs at the 60-hour threshold, leading to increases of up to 40 percent in average hourly labor costs. In contrast to the sharp increase in hourly wages following the 2018 minimum wage hike, the share of sub-60-hour workers continued its modest upward trend, raising questions about a causal interpretation. I offer an alternative explanation: compliance with institutions that induce nonlinear labor cost schedules improved substantially during this period, particularly in sectors most exposed to minimum wage increases. These findings suggest that the estimates of the effects of minimum wage increases may be biased due to concurrent improvements in compliance that are correlated with exposure to the minimum wage.

• Developed from Chapter 5 of Drivers of Part-time Work Growth and Policy Recommendations (KDI Research Monograph, forthcoming)