RESEARCH IN PROGRESS

Highways and Segregation: Evidence from the US South [JMP coming soon]

I construct a county-level panel of racial dissimilarity indices across the U.S. South, combining historical full-count Census data with modern ACS data. To estimate the impact of Interstate highways on segregation, I employ two complementary strategies: (i) a difference-in-differences design and (ii) a propensity score design based on a spatial model of road network planning. The propensity score approach yields similar estimates to the difference-in-differences approach, while using only cross-sectional quasi-experimental variation in highway placement. Leveraging this design, I further explore how Interstate construction influenced alternative measures of segregation, which speak to the spatial dimensions of racial sorting.

The Effect of Interstates on Regional Development: Novel RD and IV Approaches [slides] 

From planning documents, I discover that cities with populations over 50,000 in 1940 are more likely to be included in the Interstate system. I use this discontinuity to create a bias-adjusted instrument for counties’ distance to an Interstate, following Borusyak & Hull (2023). For many counties, their distance to an Interstate is affected by the plausibly exogenous inclusion of counties near the population discontinuity, however exposure to this exogenous shock is non-random. To adjust for non-randomness, I simulate plausible counterfactual networks by permuting which counties near the cutoff are included in the network. By controlling for the average distance of counties to these counterfactual networks, I isolate identifying variation that arises from the discontinuity at an arbitrary cutoff.