Dongwoo Kim

We study rare special cases of existing employers opting into Social Security. We use restricted teacher-level data from Texas to analyze how public school districts that opt into Social Security handle the increased tax burden. Using event study and synthetic control methods, we find suggestive evidence that districts gradually reduce salary growth over time and reach a long-run salary difference that matches or exceeds the Social Security tax. We do not find evidence of changes in teacher employment. These results reveal potential implications of the Social Security opt-in for currently uncovered public sector workers, as well as local and state governments.

We study the incidence of Social Security taxes on teacher wages and employment. On average, we estimate teachers with Social Security coverage take home 9.6 percent less in wages than observationally similar teachers in similar districts without Social Security coverage. This accounts for about three-fourths of the 12.4-percent total Social Security tax. Moreover, our analysis suggests this is likely a lower-bound estimate of the true incidence of Social Security taxes – under reasonable assumptions, we cannot rule out full (100%) tax incidence on teacher wages. We find no evidence of tax incidence on teacher staffing levels.

We use a difference‐in‐differences design to study the effect of opioid use on traffic fatalities. Following Alpert et al., we focus on the 1996 introduction and marketing of OxyContin, and we examine its long‐term impacts on traffic fatalities involving Schedule II drugs or heroin. Based on the national fatal vehicle crash database, we find that the states heavily targeted by the initial marketing of OxyContin (i.e., non‐triplicate states) experienced 2.4 times more traffic fatalities (1.6 additional deaths per million individuals) involving Schedule II drugs or heroin during 2011–2019, when overdose deaths from heroin and fentanyl became more prominent. We find no difference in traffic fatalities until after the mid‐2000s between states with and without a triplicate prescription program. The effect is mainly concentrated in fatal crashes with drug involvement of drivers ages between 25 and 44. Our results highlight additional long‐term detrimental consequences of the introduction and marketing of OxyContin.

We use a regression discontinuity design to study the effect of the COVID‐19 lockdown on traffic accidents. Based on administrative data from Louisiana, we find that the lockdown order led to a significant decrease in traffic accidents (−47%), including accidents involving injury (−46%) and ambulance (−41%). We also find evidence of heterogeneous changes in the decline of drivers involved in accidents, with a smaller decline among individuals aged 25 to 64, male, and nonwhite drivers.

A majority of career teachers in Missouri defined benefit pension plan reach their pension wealth peak before their 31^st year of service. The 2002 pension enhancement in Missouri generates a local gain in pension wealth that is lower than the peak and also creates an eligibility milestone at the 31^st service year. To test whether the 31^st year enhancement affects retirement timing decisions for mid- to late-career teachers, I use administrative data of Missouri teachers and employ difference-in-differences models. I find that the 31^st year enhancement reduces the likelihood of retirement at early and full retirement eligibilities, and helps retain experienced teachers.

Recent papers have documented positive externalities of Medicaid expansions on several non‐health related variables, such as crime, financial stress, child support, and child abuse. In this paper, we investigate the relationship between access to public health insurance and foster care admissions following state decisions to expand Medicaid coverage after the Affordable Care Act. Over 70% of all foster care admissions are related to child abuse incidents, which have been found to decrease following the Medicaid expansions. Our results suggest that the Medicaid expansions are associated with a large decrease in foster care admissions, driven by neglect incidents.

I use a city-level fixed effects model with city-specific linear trends that exploits different trends in violent crime rates among 229 major cities in the US from 1986 to 2010. Findings suggest that a 10 percent increase in the violent crime rate is associated with 0.2 and 0.4 percent decreases in enrollment in grades 11 and 12, respectively. However, the association of violent crime rate with grade 9 enrollment is not statistically significant. The results show that violent crime rate is negatively associated with high school enrollment levels, concentrated in grades 11 and 12.