Publications by authors named "Kanghyock Koh"

The Medicaid coverage "cliff" occurs when Medicare beneficiaries with household income exceeding 100% of the federal poverty level lose eligibility for supplemental Medicaid coverage. Using a regression discontinuity design with data from Medical Expenditure Panel Survey and National Health and Nutrition Examination Survey for 2007-2019, we demonstrate that the cliff increases out-of-pocket spending by 25% and the probability of experiencing problems paying medical bills by 44.4% without decreases in overall health care spending.

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We test the income fungibility assumption from standard economic theory by analyzing spending responses to South Korea's labeled COVID-19 stimulus payments. We exploit unique policy rules for identification: (1) recipients cannot use payments outside their province of residence, and (2) they can only use payments at establishments in pre-specified sectors. Using data on card transactions in Seoul, we find that households do not consider stimulus payments fungible.

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We examine the short-term impact of COVID-19 on consumption spending and its underlying mechanisms using individual-level monthly panel data from Singapore. Although Singapore's case fatality rate was one of the lowest in the world in the early stage of the pandemic (0.05%), we find that the COVID-19 pandemic reduced household consumption spending by almost one quarter at its peak, with a larger response from households with above-median wealth.

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Background: The COVID-19 pandemic has challenged the capacity of healthcare systems around the world and can potentially compromise healthcare utilization and health outcomes among non-COVID-19 patients.

Objectives: To examine the associations of the COVID-19 pandemic with healthcare utilization, out-of-pocket medical costs, and perceived health among middle-aged and older individuals in Singapore.

Method: Utilizing data collected from a monthly panel survey, a difference-in-differences approach was used to characterize monthly changes of healthcare use and spending and estimate the probability of being diagnosed with a chronic condition and self-reported health status before and during the COVID-19 outbreak in 2020.

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We study the role of access to health insurance coverage as a determinant of individuals' subjective well-being (SWB) by analyzing large-scale healthcare reforms in the United States. Using data from the Behavioral Risk Factor Surveillance System and Panel Study of Income Dynamics, we find that the 2006 Massachusetts reform and 2014 Affordable Care Act Medicaid expansion improved the overall life satisfaction of Massachusetts residents and low-income adults in Medicaid expansion states, respectively. The results are robust to various sensitivity and falsification tests.

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We estimate the economic impact of South Korea's targeted responses to the large-scale COVID-19 clusters in a highly concentrated business area (Guro) and a highly concentrated entertainment area (Itaewon) in Seoul, respectively. We find that foot traffic and retail sales decreased only within a 300 m radius and recovered to their pre-outbreak level after four weeks in the case of the Guro cluster. The reductions appear to be driven by temporary business closures rather than by citizens' risk avoidance behavior.

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We estimate the causal effects of household income on self-reported health status by exploiting random variations in the amount of lottery prizes won. We find that a S$10,000 (US$7,245) increase in income via lottery wins improves individuals' health by a standard deviation of 0.18.

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A delayed school start time (DSST), achieved by removing zero period, could change students' other time use during school as well as other forms of human capital accumulation. Using difference-in-differences, we find evidence that a DSST in South Korea reduced the time students spent in gym class without worsening students' health status. Combined with previous studies that provided evidence that DSSTs increased students' test scores, our results imply that a DSST can increase students' academic achievement without reducing other forms of human capital accumulation, although schools might change students' other time use.

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Background: Lifestyle modifications are associated with better outcomes for patients with diabetes. Patients' awareness of having diabetes may promote lifestyle changes, but there is limited evidence to support this assertion. This study examined whether a report of physician-diagnosed diabetes is associated with dietary changes and efforts to lose weight.

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During a recession, cost-sharing of employer-sponsored health benefits could increase to reduce labor costs in the U.S. Using a variation in the severity of recession shocks across industries, I find evidence that the enrollment rate of high deductible health plans (HDHPs) among workers covered by employer-sponsored health benefits increased more among firms in industries that experienced severe recession shocks.

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Do children with lower test scores benefit more from breastfeeding than those with higher scores? In this paper, I examine the distributional effects of maternal breastfeeding on the cognitive test scores of 11,544 children who were born in 2000 and 2001 in the United Kingdom using a semiparametric quantile regression model. I find evidence that maternal breastfeeding has larger positive impacts on children with lower test scores. Effects for children below the 20th percentile are about 2-2.

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