Research

The opioid crisis has had adverse public health effects, with the White population disproportionately affected in its initial phase, yet our understanding of the effects of the crisis on neighborhood inequality remains underdeveloped. This study examines how opioid-related policies transform neighborhood poverty by analyzing the 2010 reformulation of OxyContin---a supply-side intervention to reduce prescription opioid abuse. It argues that the reformulation inadvertently prompts impoverished opioid users to switch to heroin and relocate to neighborhoods with heroin availability, leading to the emergence of White high-poverty neighborhoods. Using a continuous difference-in-differences design, it finds that following the reformulation, White high-poverty neighborhoods emerge at higher rates in counties with initially high opioid dispensing rates compared to lower-rate counties. This effect is absent in non-White neighborhoods and amplified in neighborhoods with initially high housing vacancy. Within high-vacancy areas in high-opioid counties, heroin availability increases post-reformulation, and the resulting high-poverty neighborhoods stem from the relocation of the poor rather than increasing the overall poor population. Taken together, the post-reformulation emergence of White high-poverty neighborhoods is due to a sorting process into areas where heroin becomes available. The study highlights the unintended consequences of supply-side drug policy on the geographic distribution of poverty along racial lines.

Japan’s Yakuza Exclusion Ordinances (YEOs) are indirect enforcement that cuts criminal groups' lawful ties, severing revenue streams. Our model predicts the YEOs reallocate effort from traditional rackets to organized fraud schemes with non-yakuza criminal groups, increasing sophistication level without proportionate growth in case counts. This is particularly salient in low yakuza-competition areas where dominant groups internalize fraud profits. Guided by this model, we empirically find the YEOs raise financial damage while leaving case counts largely unchanged,with stronger effects in low-competition areas. Complementarity between yakuza and non-yakuza groups amplifies this shift. Arrest data confirm yakuza transitioning from extortion to fraud.

As the United States undergoes demographic shifts where multiple racial and ethnic groups increasingly coexist, understanding how these changing compositions affect residential segregation is crucial. We demonstrate that segregation responds to the ordinal ranking of minority groups---their relative positions by population share---not only group population sizes. We use U.S. census data from 1990, 2000, and 2010 to show that segregation follows rank-triggered tipping: segregation increases when minority groups change their relative ranking order. Holding group population shares constant, both across groups within the same county and within the same group over time, a higher rank is associated with higher segregation. Ranks concentrate neighborhood change in specific locations---White flight and minority clustering intensify in census tracts where the higher-ranked group already has substantial presence. Our findings reveal that residential sorting operates through two complementary mechanisms: traditional share-based tipping (based on absolute population sizes) and rank-triggered tipping (based on relative group size). These findings help explain the persistence of segregation across different minority groups and temporal variation in segregation within the same locations, advancing our understanding of how demographic diversity translates into segregation.

This study investigates whether industry-specific shocks propagate through the broader criminal economy when specific criminal groups are embedded in affected sectors, generating persistent changes in organized crime. It focuses on Japanese organized crime, the yakuza, and the 1960s energy transition from domestic coal to imported oil, which triggered widespread mine closures. Some yakuza groups operated in coal mining as labor brokers, protection racketeers, or contractors. I document persistence in yakuza-related conflicts following the energy transition, with greater effects in areas with historical presence of mining-linked yakuza groups and alternative economic rents. Underlying this persistence, the composition of local organized crime shifted following the transition: arrests of mining-linked yakuza fell while arrests of non-mining yakuza rose as rival yakuza groups entered coal-affected areas to contest territory. In the 21st century, areas more exposed to transition-induced mining job losses exhibit substantially higher yakuza presence. However, yakuza exclusion ordinances enacted in the 2010s partially broke this persistent cycle by restricting organizational reallocation across all yakuza groups. Taken together, negative industry-specific shocks can trigger territorial restructuring that hardens into persistent criminal geography.

Despite being the least suburbanized group, Black suburbanization doubled from the 1970s to the 2010s. This study traces a portion of the rise of Black suburbanization to the emergence of crack cocaine in mid-1980s and early 1990s. It argues that the outbreak of the crack epidemic---a race- and location-specific negative shock that severely affected inner-city Black communities---triggered migration capacity, thereby driving the long-term Black flight to the suburbs. Analyses using metropolitan, individual, and census tract level data collectively produce the following results. Two decades post-crack emergence, the trend of Black suburbanization still escalated at a greater rate in high crack exposure areas. Black suburbanization increased particularly in areas with a high concentration of initial migration flows, where Black migrants from their origin cities relocated to a select few suburban destinations. Black suburbanization following crack exposure was not limited to inner-ring suburbs or disadvantaged neighborhoods. Quantifying the magnitude, the study reveals that the crack epidemic led to the suburbanization of nearly 1 million Black people. The study demonstrates the understudied role of the crack epidemic in shaping the racial geography of the United States in the long run.