My dissertation studies labor market structure and evaluates effects of policies relating to transportation improvements and immigration enforcement in different countries including Germany, the Untied States, and China. Specifically, I examine thenature and extent of labor market frictions, explore the causes and consequences, as well as study the role in policy evaluations.In the first chapter, I investigate one potential source of labor market frictions from limited labor mobility by examining how integrating labor markets through improved transportation infrastructure affects both wages and the allocation of workersacross establishments. I take advantage of the expansion of the High-Speed Rail in Germany, which connected medium-sized di...