Research

Using a panel of Chinese cities from 1999 to 2018, this study examines how foreign direct investment (FDI) and road infrastructure jointly influence local economic growth. Within a human-capital-augmented Solow framework, the analysis shows that FDI is positively associated with growth in GDP per capita, and that this relationship strengthens when cities possess more extensive road networks. The results suggest that transportation infrastructure facilitates the diffusion of technologies and productivity spillovers introduced by foreign firms, thereby amplifying the growth effects of FDI. The complementary interaction between FDI and road infrastructure is most evident in technology-intensive cities, coastal regions, and top-tier urban areas. Multiple robustness checks, including alternative specifications and estimation approaches, support the consistency of these findings.

The paper studies the effect of the high-speed rail (HSR) service on the mental health of individuals aged 45 and older. I use historical documents and ArcGIS Pro to produce the railway map of the late Qing Dynasty (1911) and use it as an instrument for the modern HSR network in China. I find that the HSR service significantly improves the mental health of middle-aged and elderly people, and the causal impact is larger for urban than for rural residents. I also explore and find supporting evidence for three channels of influence: income, access to medical services and in-person interactions. The HSR increases employment opportunities and, hence, individual income, improves the accessibility of medical resources outside the local area, and increases the frequency of in-person visits by children who do not live in the same city as their parents.

While federal regulation has delivered major improvements in air and water quality, sensory pollutants - such as traffic noise and artificial nighttime illumination - remain largely unregulated and understudied. These environmental stressors are pervasive in urban infrastructure and increasingly linked to mental health risks, yet little causal evidence exists on their impacts. We provide the first national-scale analysis of the effect of ambient roadway noise and nighttime light pollution on mental health. We link restricted-use survey microdata from approximately 14,000 respondents in the United States to high-resolution sensory exposures, and leverage natural variation in topography, temperature, and atmospheric conditions to isolate the causal effect of roadway noise and nighttime light on self-reported mental health. Both pollutants exert statistically and economically meaningful effects: road noise increases the likelihood of mild psychological distress by 11%, while light pollution increases it by 13%. These effects are partially mediated through reductions in sleep duration. Welfare losses are up to $25 billion annually.