This dissertation consists of three chapters. In Chapter 1, I study the impact of partisan leaders on traffic stop policing behaviors in North Carolina. Using a difference-in-differences design that exploits sheriff turnovers, I find that offices with a Democrat-to-Republican sheriff turnover rather than a Democrat-to-Democrat sheriff transition have an increase of black drivers’ share in traffic stops by 3.2 percentage points, a 13.5% increase compared to baseline. Decomposing the changes in black driver's share along two dimensions: stop purposes and officers, I find that the increase is driven by changes within safety stops instead of investigation stops, and driven by changes in incumbent officers' tendency to stop black drivers. The increase in racial disparities is not accompanied by an increase in unconditional hit rates.

In Chapter 2, in joint work with Samuel Krumholz, we study the impact of partisan leaders on the political composition of law enforcement agencies in the United States using elected sheriffs in North Carolina as a case study. Using a difference-in-differences design, we find that offices shifting from a Democrat to Republican sheriff experience a 9 percentage point (27%) decrease in the Democratic share of Sheriff deputies relative to counties experiencing a Democrat-to-Democrat turnover. This change is driven both by existing Democratic deputies disproportionately changing their party registration and an increase in the share of Republican deputies among the entrants. Overall, we provide new evidence that leaders can shape the personnel's political composition not just by hiring but by inducing party switches.

In Chapter 3, in joint work with Ming-Jen Lin and Tzu-Ting Yang, we examine the causal effects of textbook content on individuals' national identity, by exploiting a curriculum reform that introduced a new perspective on Taiwan's history for students entering junior high school after September 1997. Using a repeated nationally representative survey and a regression discontinuity design, we show that students exposed to the new textbooks were more likely to hold exclusive Taiwanese identity rather than dual identity (i.e., Taiwanese and Chinese). The effect was greater for academic track students and those living in neighborhoods where fewer people identify as Taiwanese. We find little impact of the new curriculum on people's political preferences related to Taiwan's independence. Finally, we find that the probability of reporting as Taiwanese among old textbook readers converges with that of people reading new textbooks in the long run since the perspectives of old textbooks are in conflict with the recent social trends.